• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/180

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

180 Cards in this Set

  • Front
  • Back
what are the three types of immunoglobulin gene modifications?
1. V-(D)-J recombination
2. somatic hypermutation
3. class-switching
what are the recombination activating genes?
RAG1 and RAG2
what is AID?
activation-induced cytidine deaminase

the key enzymatic mediator of somatic hypermutation, gene conversion and class-switching
how does AID work?
(activation-induced cytidine deaminase) deaminates selected cytosines in certain mRNAs, changing the cytosines to uracils and thereby altering the protein-encoding instructions of the targeted messenger RNA. (in somatic hypermutation and class-switching)
what four elements does class-switching depend on?
1. switch regions
2. a switch recombinase
3. cytokine signals (which dictate the isotype to which the B-cell switches)
4. the enzyme AID
there is a switch site/region located upstream of each CH segment except for which one?
Cd - Delta
where are variable-region gene segments found?
in germ-line DNA
each recombination signal sequence (RSS) contains what three things?
1. a conserved heptamer sequence
2. a conserved nonamer sequence
3. either a 12bp (one turn) or a 23bp (two turn) spacer
in what order are constant heavy chain gene segments arranged? why?
u, d, y, e, a

because of the sequential expression of Ig classes in the course of B cell development & the initial IgM response of a B cell to its first encounter with an antigen
what are the four ways that junctional diversity is generated at the V-J and V-D-J coding joints?
1. variation in the cleavage of the hairpin to generate P-nucleotides
2. variation in the trimming of the coding sequences
3. variation in N-nucleotide addition (heavy chains)
4. flexibility in joining in the coding sequences
what does allelic exclusion ensure?
a single antigenic specificity
what are the seven means of antibody diversification?
1. multiple germ-line gene segments
2. combinatorial V-(D)-J joining
3. junctional flexibility
4. P-addition
5. N-addition
6. somatic hypermutation
7. combinatorial association of light and heavy chains
does rearrangement of Ig genes occur before or after transcription?
before
when does a B cell become immunocompetent?
following productive rearrangement of variable region heavy-chain AND light-chain gene segments in germ-line DNA
do b-cells need APC's?
no!
do Th-cells need APC's?
yes! MHC class II presentation!
the repertoire of antigens to which a given Tc or Th cell can bind is determined by what?
MHC molecules expressed on cell
natural killer cells express receptors for which class of MHC antigens?
class I MHC
which branch of the immune system does MHC play a role?
both cell-mediated and innate
what is the major histocompatibility complex?
a collection of genes arranged on a continuous stretch of DNA on chromosome 6 in humans and 17 in mice, that encodes 3 classes of molecules
what do class III MHC genes encode?
various secreted proteins that have immune function, such as components of the complement
class III MHC products include what?
complement components C4, C2, and factor B as well as several inflammatory cytokines, including tumor necrosis factor (TNF)
a set of alleles inherited together is called what?
a haplotype -an individual inherits one haplotype from the mother and one haplotype from the father
the loci constituting the MHC are highly polymorphic. what does this mean?
many alternative forms of the gene, or alleles, exist at each locus
what does it mean if inbred mouse strains are syngeneic?
syngeneic mice are identical at all genetic loci
what does it mean if inbred mouse strains are cogenic?
cogenic mice are genetically identical except at a single genetic locus or region
what is the specific composition of a MHC class I molecule?
a 45-KDa alpha chain associated noncovalently with a 12-KDa beta-2-microglobulin molecule
the alpha chain of class I MHC molecules is a transmembrane glycoprotein encoded for by what?
polyphorphic genes within the A, B, C regions in the human HLA complex and within the K and D regions of the mouse H-2 complex
the beta-2-micoglobulin protein of MHC class I molecules is encoded by what?
a highly conserved gene located on a different chromosome
how is the alpha chain of MHC class I molecules anchored in the plasma membrane?
by its hydrophobic transmembrane segment and hydrophilic cytoplasmic tail
structural analysis has revealed that the alpha chain of class one MHC molecules is organized into what?
3 external domains (a1, a2 and a3)
beta-2-microglobulin is similar in size and organization to which of its alpha counterparts? despite being of similar size and organization, in what ways does b2 differ?
a3; b2 microglobulin does not contain a transmembrane region and is noncovalently bound to the class I glycoprotein.
where does papain cleave MHC class I molecules?
near transmembrane domain -releasing the entire extracellular a1, a2, a3 and b2 portions of the molecule
purification of the extracellular portion of MHC class I reveals what?
two pairs of interacting domains- a1 and a2 (membrane distal) and membrane proximal a3 and b2
which part of the MHC class I molecule form the peptide-binding cleft?
a2 and a1
the peptide binding cleft on MHC class I molecules can bind a peptide of what size?
8-10 amino acids
how is the initial assembly of class I molecules believed to occur?
by the interaction of beta-2-microglobulin with the folding class I alpha chain.
what happens after the initial interaction of beta-2-microglobulin with the folding class I alpha chain in class I MHC molecules?
the metastable "empty" alpha chain and beta-2-microglobulin dimer is stabilized by bind of a peptide to binding cleft and the complete molecular complex is transported to the cell surface for presentation
what happens in the absence of beta-2-microglobulin (in MHC class I molecules)?
the class I alpha chain is not expressed on the cell surface
what do Duadi tumor cells demonstrate?
Daudi tumor cells can not synthesize beta-2-microglobulin and are therefore unable to express a functional alpha chain on cell surface/membrane
specifically, what are class II MHC molecules composed of?
a 33-kDa alpha chain and a 28-kDa beta chain that associate by noncovalent interactions
sequence data reveal homology between what regions of MHC class I molecules and the constant-region domains of immunoglobulins?
alpha 3 domain and b2 microglobulin
what region (proximal or distal) on both class I and class II MHC molecules has sequence similarity with the constant domain of immunoglobulins and are therefore classified in the immunoglobulin superfamily?
the proximal domains

in MHC I: a3 and b2 microglob.
in MHC II: a2 and b2
each region of class I and II MHC molecules are encoded for by what?
separate exons
class I MHC genes all contain what exons?
a 5' leader encoding signal peptide
a1, a2, & a3 domains
the transmembrane region
2 3' terminal regions encoding cytoplasmic domains
what is the purpose of the 5' leader sequence in MHC I genes?
encodes signal peptide that facilities insertion of the alpha chain into endoplasmic reticulum, after which it is cleaved/removed by proteolytic enzymes.
what exons do class II genes contain?
leader exon
an alpha 1 or beta 1 exon
an alpha 2 or beta 2 exon
transmembrane exon
one or more cytoplasmic exons
how many different MHC I and MHC II molecules can an individual human express?
6 different MHC class I
12 different MHC class II
is peptide binding by class I and class II MHC molecules as specific as antigen binding by antibodies and T cell receptors?
no! a given MHC molecule can bind a numerous different peptides, and some peptides can bind to several different MHC molecules
why is MHC-peptide binding not as specific as antigen binding to antibodies or T cell receptors?
because MHC molecules need to be able to present an enormous array of different antigenic peptides to T cells
what is the peptide binding domain in class I molecules?
a1-a2
what is the peptide binding domain in class II molecules?
a1-b1
the binding cleft of class I molecules is blocked at both ends, whereas the cleft is open-ended in class II molecules. What are the consequences of this?
1. MHC I bind peptides between 8-10 AA, while MHC II bind longer peptides (13-18AA)

2. Class I binding requires that the peptide contain specific AA residues near N and C terminus
__________ peptides bind to class I MHC molecules with a higher affinity than do peptides that are either longer or shorter, suggesting that this peptide length is most compatible with the closed-ended peptide binding clefts in class I molecules.
nonameric (9 AA)
anchor residues that interact with class I molecules tend to be what?
hydrophobic amino acids (leucine, isoleucine) in carboxyl terminus
where does the main contact between class I molecules and peptides occur?
residue 2 at the amino terminal end and residue 9 at the carboxyl terminus of nonameric peptide
what type of bonding attaches class I molecules to anchor residues (~ 2 and 9)?
hydrogen bonding
from where are most of the peptides associated with class II MHC molecules derived?
self membrane bound proteins or foreign proteins internalized by phagocytosis or receptor mediated endocytosis and then processed through the endocytic pathway.
does peptide bound to MHC class I or II molecules bulge when bound?
class I
from where does the diversity of MHC within a species stem?
from polymorphism -the presence of multiple alleles at a given genetic locus within the species.
the enormous polymorphism in the MHC has been generated by what?
1. recombination
2. point mutation
3. gene conversion
where does the most polymorphic variability exist in MHC molecules?
binding domains! (a1-a2 & a1-b1)
the highest level of class I molecule expression is by what cell type?
lymphocytes
the lowest levels of class I molecule expression is by which cell types?
fibroblasts, muscle cells, liver hepatocytes, and neural cells

sperm cells and neurons do not seem to express MHC class I molecules at all
what sort of genetic expression occurs regarding MHC molecules?
MHC molecules are codominatly expressed- heterozygous individuals express both allele gene-products at each MHC locus.
what are two class II transcriptional activators/factors? defects in these transcription factors result in what?
CIITA and RFX- defects result in bare lymphocyte syndrome (lack class II molecules on cells)
MHC expression is regulated by what?
1. transcription factors
2. cytokines
which cytokines have been shown to increase expression of class I molecules?
alpha, beta, gamma interferons and tumor necrosis factor
how does gamma interferon increase expression of class I molecules?
IFN-y induces the formation of a transcription factor that binds to the promoter sequence flanking the class I MHC genes (up and down regulation)
what effect doe IFN-y have on the expression of class II molecules?
IFN-y induces expression of class II transcriptional activator CIITA, increasing the expression of class II molecules on a variety of cells, including non-antigen presenting cells!
what effect does IL-4 have on resting B-cells?
induces class II molecule expression
which cytokines down regulate class II molecule expression?
on b cells: IFN-y

corticosteroids and prostaglandins decrease expression of class II MHC molecules
what are the two explanations proposed to account for the variability in immune responsiveness observed among different haplotypes?
1. determinant-selection model
2. holes-in-the-reportoire model
what is the determinant-selection model?
a model proposed to account for the variability in immune responsiveness among different haplotypes that states that different class II molecules differ in their ability to bind antigen.
what is the holes-in-the-reportoire model?
a model proposed to account for the variability in immune responsiveness among different haplotypes that states that T cells bearing receptors that recognize antigens closely resembling self antigens may be eliminated during thymic selection.
what is self-MHC restriction?
the constraint by which CD4 and CD8 T cells can only recognize antigen when presented by a self-MHC molecule
what experiment demonstrated class II MHC restriction?
A. Rosenthal and E. Shevach exposed a strain of guinea pigs to an antigen, then collected macrophages expressing the antigen on their surface and exposed them to Tcells from the same strain, a different strain, and an F1 cross between the two. Then measured T-cell proliferation and found that Th-cells are only activated and proliferate in the presence of antigen presented on macrophages that share the same class II MHC alleles as T cell.
what experiment demonstrated CD8+ MHC class I-restriction?
mice were infected with LCM and spleen cells were collected and Tc-cells specific for the virus were isolated and exposed to virus-infected cells of the same or different haplotype. Killing only occurred in same haplotype: Tcell and virus-infected cell must share common class I molecule encoded by K or D regions of the MHC
cells that display peptides associated with class I MHC molecules to CD8+ T-cells are called _________ cells.
target cells
cells that display peptides associated with class II MHC molecules to CD4+ T-cells are celled _______ cells.
antigen presenting cells
what are the three professional APC's?
dendritic cells, macrophages, and B lymphocytes
which APC is the most effective? why?
dendritic cells- because they can activate naive Th-cells via their costimulatory activity and the fact that they constitutively express a high level of class II MHC molecules
intracellular proteins are degraded into short peptides by a cytosolic proteolytic system present in all cells, the ______________.
proteosome
what is ubiquitin?
a small protein that attaches to proteins targeted for proteolysis in a 26s proteosome which cleaves peptide bonds in an ATP-dependent process.
how are ubiquitin-tagged proteins degraded?
in 26s proteosome
what is an immunoproteosome?
a proteosome found in addition to the normal proteosome found in all cells that is the same size, but is found in virus-infected cells so it's thought to play a role in class I presentation
which cytokines can induce immunoproteasome activity?
TNF-a & interferon-y
what is TAP?
a transmembrane heterodimer protein made up of TAP1 and TAP2 that transports peptides from the cytoplasm to the RER where class I molecules are synthesized
does TAP require ATP?
yes
what two features indicates that TAP is optimized to transport peptides that will interact with class I MHC molecules?
1. TAP favors proteins with hydrophobic or basic carboxyl-terminal ends, the preferred anchor residues for class I MHC molecules.

2. TAP has an affinity for peptides containing between 8-16 AA (aminopeptidases in ER trim to optimal 9AA size)
TAP has an affinity for peptides containing between 8 and 16 AA, but the optimal size for the binding cleft of MHC class I molecules is 9 AA. How is this resolved?
aminopeptidases present in the ER, such as ERAP, trim peptides to optimal lengths
what are the chaperones involved in the assembly and stabilization of class I MHC molecules?
calnexin
calreticulin & tapasin
ERp57 (enzymatic activity)
how does ERp57 contribute to the assembly/stabilization of class I molecules?
ERp57 forms a disulfide bond to the chaperone tapasin and noncovalently associates with calreticulin to stabilize interaction and allow for release of alpha chain and b-2-microglobulin after acquisition of a peptide
how do ERAP1 and ERAP2 work?
they are aminopeptidases in the ER that function during the assembly of class I molecules.

ERAP1 cleaves peptides longer than 8 AA to optimum size and has little affinity for peptides less than 8 AA.

ERAP2 on the other hand, degrades peptides of any size to eliminate peptides not suited for class I binding
following stabilization via chaperones and ERp57, binding of peptide of productive size, and dissociation of chaperones and ERp57, where does the complex go next?
cell surface via the golgi complex
how do B-cells internalize antigen?
receptor mediated endocytosis via antigen-specific membrane antibodies as receptor
what is the invariant chain?
in class II molecule assembly-protein trimer that interacts with the peptide-binding cleft of class II molecules preventing any premature binding of endogenous peptide, assisting in folding of alpha and beta chains, their exit from the RER, and transport through the endocytic processing pathway
what is CLIP?
a part of the degraded invariant chain in class II assembly that remains bound to the peptide binding groove until actual peptide binds
what is HLA-DM? HLA-DO?
HLA-DM is a nonclassical, nonpolymorphic class II MHC molecule that is required for the exchange of CLIP with antigenic peptides

HLA-DO is also nonclassical and nonpolymorphic, but it binds to HLA-DM and lessens its efficiency in the exchange between CLIP and antigenic peptide
what is cross presentation?
when exogenous antigen is presented by class I molecules instead of class II
how are non-peptide antigens presented?
by CD1 family of nonclassical class I molecules that associate with beta-2-microglobulin and share a structure similar to that of class I MHC molecules
what was Tonegawa's experimental contribution that lead to the confirmation of gene rearrangement?
he performed an experiment in which he took DNA from myeloma cells and embryonic cells and used restriction endonucleases to generate gene fragments which he separated by size and analyzed for the ability to hybridize with radiolabed mRNA probes
variable region gene rearrangements occur in an ordered sequence during B-cell maturation in the bone marrow. Genes for which chain are rearranged first?
the heavy-chain variable-region genes rearrange first, THEN the light chain variable-region genes.
recombination signal sequences (RSSs) are found where?
3' to each V gene segment, 5' to each J segment and on both sides of each D segment
what is an RSS?
recombination signal sequence: contain a conserved palindromic heptamer and a conserved AT-rich nonamer sequence separated by an intervening sequence of either 12 or 23 base pairs
what are the components of an RSS?
a palindromic heptamer and a AT-rich nonamer separated by an intervening sequence of either 12 or 23 base pairs (one-turn or two-turn)
what is the significance of the fact that signal sequences having a one-turn spacer can only join with sequences having a two-turn spacer?
this joining rule ensures that segments are joined properly and in the correct order
where does VDJ recombination occur?
at the junctions between RSSs and coding sequences
what are VDJ recombinations catalyzed by?
VDJ recombinases
how is junctional diversity at the V-J and V-D-J coding joints generated?
1. variation in cleaving hairpin to generate P-nucleotides
2. variation in trimming of the coding sequences
3. variation in N-nucleotide addition (heavy chain)
4. flexibility in joining the coding sequences
what is a consequence of imprecise joining of coding sequences?
generation of non-productive reading frames, interrupting translation.
what does allelic exclusion ensure?
that functional B cells never contain more than one VDJ and one VJ unit
what is p-addition?
palindromic sequence added to the coding joint following cleavage of the hairpin formed during deletional inversion
physically, where does somatic hypermutation usually occur?
within germinal centers- structures that form within secondary lymphoid organs within a week or so of immunization with an antigen that activates t-cell dependent b-cell repsonse
what are the most common mutations in somatic hypermutation?
nucleotide substitutions
where do most somatic hypermutations occur?
in the CDRs of the Vh and Vl sequences, where they are most likely to influence the overall affinity for antigen
somatic hypermutation is mediated by what?
AID
class switching is mediated by what?
AID
what does AID mediate?
class switching and somatic hypermutation
there is a switch region upstream of all heavy constant segments except which one?
delta
IL-4 induces class switching from ____ to ____ or _____.
C mew to C gamma 1 or epsilon
on what four elements does the process of class switching depend?
1. switch regions
2. switch recombinases
3. cytokine signals to dicate what isotype to switch to
4. AID (activation induced cytidine deaminase)
what are the 3 types of Ig gene modification?
1. V (D) J recombination
2. somatic hypermutation
3. class (isotype) switching
what are the four ways increase junctional diversity?
1. variation in trimming hairpin/P-addition
2. variation in trimming of coding sequences
3. variation in N-nucleotide addition (heavy only)
4. flexibility in joining coding sequences (productive/nonproductive)
specifically, what does AID do?
AID deaminates certain cytosines in mRNA, converting them into uracils and thereby altering the protein-encoding instructions of the mRNA
how can a B-cell simultaneously express IgM and IgD and produce secreted or membrane bound forms of a particular Ig?
processing of heavy chain primary transcript can yield several different mRNAs
which immunoglobulins have a hinge region? (3 constant heavy regions)
IgG, IgD, IgA
which immunoglobulins have no hinge region? (4 constant heavy regions?
IgM and IgE
what determines whether an Ig is produced in secreted or membrane bound form?
differential processing/splicing: which poly-A site is cleaved (if first one, then secreted is formed because M1 and M2 which code the transmembrane and cytoplasmic segments are excised) if poly-A site 2, then membrane bound form is produced containing M1 and M2.
naive b-cells produce only which type of Ab? differentiated plasma cells produce which type of Ab?
naive -membrane bound

plasma -secreted
what is BiP?
Ig heavy-chain binding protein: binds to incompletely assembled antibody molecules in the ER, where they are retained and marked for proteolysis by ubiquitin
where are proteosomes found?
in the cytosol
what are the two major classes of cis-regulatory sequences in DNA that regulate transcription of Ig genes?
1. promotors (upstream of tx start)
2. enhancers (upstream or downstream of tx start)
what is E2A?
regulator of transcription- a gene that produces two proteins required for b-cell development
what is the difference between a chimera and a humanized Ab?
chimera is composed of human constant regions and mouse monoclonal Ab variable regions

humanized Ab is entirely human except for the CDR regions which are of mouse monoclonal Ab origin
what is an abzyme?
a monoclonal Ab that catalyzes reactions (dissolve blood clots, cleave viral glycoproteins)
what effect do acute phase proteins have on complement?
acute phase proteins activate the complement cascade
what are the four basic complement functions?
1. lysis
2. opsonization
3. activation of inflammatory response
4. clearance of immune complexes by cells in the spleen and liver
the soluble proteins and glycoproteins that constitute the complement system are synthesized mainly by what?
liver hepatocytes
in the three complement pathways, all steps after the formation of C_ are the same, leading to the production of the ____.
C5 ...leading to the production of the membrane attack complex, or MAC
binding of antigen to which classes of immunoglobulin can activate the classical complement cascade?
IgM and IgG
what induces conformational changes in the Fc portion of the IgM molecule that exposes binding site for C1? (classical complement)
formation of an Ag-Ab complex
what is C1 composed of?
C1q + (2) C1r + (2) C1s
what is the C1qr2s2 (C1) complex stabilized by?
calcium ions
each C1r and C1s component of C1 contains what two domains?
an interaction domain and a catalytic domain
what are the specific requirements for a stable C1-antibody complex to form?
each C1 macromolecule must bind by its C1q globular heads to at least 2 Fc sites!
what is the staple configuration of IgM?
pentameric IgM- because at least 3 binding sites for C1q in the Fc are exposed when bound to antigen on a target surface
can IgM in planar conformation activate complement?
no, because the C1q binding sites in the Fc are not exposed
what must be true in order to IgG to activate complement?
IgG only has only one C1q-binding site in the Ch2 domain of the Fc, so firm C1q binding only occurs when two IgG molecules are within 30-40nm of one another on a target surface, providing 2 binding sites for C1q.
what is the C3 convertase in the classic complement pathway?
C4b2a
what is the C5 convertase in the classic complement pathway?
C4b2a3b
which part of the C5 convertase binds to C5? which part cleaves C5?
the C3b portion binds C5; the C4b2a portion cleaves C5
what are the anaphylatoxins generated in the classical complement pathway?
C3a, C4a, C5a
the alternate complement pathway is a part of which branch of the immune system?
innate- does not require Ab!
the classic complement pathway is a part of which branch of the immune system ?
adaptive- requires Ab!!
what are the four serum proteins involved in the alternate complement pathway?
1. C3
2. Factor B
3. Factor D
4. properdin
if the alternative pathway does not require Ab, what activates this cascade?
cell surface constituents that are foreign to host; both gram - and gram + bacterial cell walls activate the alternative complement cascade
in the alternative complement pathway, why does C3 spontaneously hydrolyze?
due to unstable thioester bond
how is the lectin complement cascade activated?
the binding of MBL to mannose residues on glycoproteins or carbohydrates on the surface of microorganisms
what is MBL?
mannose binding lectin is an acute phase protein!

like all acute phase proteins, the concentration of MBL increases during inflammation
in the lectin complement pathway, the role of MBL is most similar to ___ in the classic complement pathway.
MBL is functionally and structurally similar to Cq1
in the lectin pathway, what are the two MBL-associated serine proteases analogous to C1r and C1s in the classical pathway?
MASP1 and MASP2
what are MASP1 and MASP2?
MBL-associated serine proteases involved in the lectin complement cascade, analogous to C1r and C1s
during the amplification step of all complement pathways in which hundreds of C3b molecules are generated, how is damage to normal host cells minimized? (theoretically C3b could bind to nearby cells, mediating damage through MAC formation)
C3b undergoes spontaneous hydrolysis by the time is has diffused 40 nm away from the C4b2a or C3bBb convertase enzymes.

and through C3 regulatory proteins encoded for by a single location on chromosome 1, called the RCA gene cluster (regulators of complement activation)
what is the RCA gene cluster?
encodes regulatory proteins that regulate C3 convertase activity in the classical and alternative pathways
C3 convertases are dissociated by which complement regulatory proteins?
C4bBP, CR1, factor H and DAF
what can be lysed by the MAC?
gram negative bacteria, parasites, viruses, erythrocytes and nucleated cells
which complement product is most important in degranulation of eosinophils?
C5a
which complement product is most important in clearance of immune complexes?
c3b
which complement product is implicated in viral neutralization?
c3b, and MAC (C5b-9)
which complement products are implicated in the degranulation of mast cells and basophils?
the anaphylatoxins (C3a, C4a, C5a)
which complement products are implicated in extravasation and chemotaxis of leukocytes at inflammatory site?
mostly C5a, but also C3a and C5b67
C3b is most often associated with which biological effects?
opsonization, viral neutralization, clearance of immune complexes (in addition to formation of the C5 convertase)
E. Coli and Salmonella are gram negative bacteria resistant to complement mediated lysis. Why so?
the presence of long polysaccharide chains in cell wall LPS, preventing insertion of MAC into membrane
how is gram-neg Neisseria resistant to complement mediated lysis?
membrane proteins form noncovalent interactions with MAC, preventing its insertion in membrane
why are most gram positive bacteria resistant to complement mediated lysis?
because of the thick peptidoglycan layer in cell wall that prevents insertion of MAC
how does the bacterial capsule of gram-positive bacteria prevent complement-mediated lysis?
acts as a physical barrier between C3b deposited on cell membrane and CR1 receptor on phagocytic cells
deficiency in the complement components has what clinical consequences?
increased susceptibility to bacterial infections and systemic lupus erythematosus, which is related to the inability to clear immune complexes
antigen coated (opsonized) with C3b binds to cells bearing which receptor?
CR1
how are immune complexes cleared from circulation?
immune complexes are coated with C3b, and bind to CR1 receptors on erythrocytes. erythrocytes then take the immune complexes to the liver and spleen to be phagocytosed