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27 Cards in this Set
- Front
- Back
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Lymphoid organs
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i. Location where maturation, differentiation, and proliferation of lymphocytes take place
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Primary lymphoid organs
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i. Organs where T and B lymphocytes first begin expression of their antigen receptors
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Bone marrow I
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1. Site of B cell maturation
2. B cells begin expressing surface immunoglobulin (slg) in the bone marrow 3. Site of hematopoiesis (sternum, vertebrae, iliac bones, and ribs) |
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Bone marrow II
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4. Hematopoietic stem cells express CD34 and stem cell antigen-1 (Sca-1)
a. Markers are used to enrich stem cells for transplantation/immune reconstitution 5. Stem cell differentiation is stimulated by CSF and IL produce by stromal cells and macrophages in the marrow |
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Thymus
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1. Site of T cell maturation
2. Precursor cells migrate from bone marrow to thymus 3. Once in thymus, T cells begin expressing surface TCR molecules 4. 3rd pharyngeal pouch a. gives rise to thymus and parathyroid 7. Bilobed 8. Maximum size at puberty |
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Cortex of thymus
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a. Contains precursor and immature T cells
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Medulla of thymus
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a. Contains mature T cells and Hassall’s corpuscles
b. Medulla+corticomedullary junction i. Elimination of autoreactive T cells |
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DiGeorge syndrome
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a. Chromosome 22q11.2 deletion
b. Born with little or no thymus c. Highly susceptible to viral infections due to lack of T cells d. Appearance similar to fetal alcohol syndrome e. Notched ears f. Gradient of presentation |
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Secondary lymphoid organs
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i. Organs where lymphocytes respond to antigens by undergoing clonal selection and proliferation
1. Spleen 2. Lymph nodes 3. Mucosa-associated lymphoid tissue (MALT) |
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Lymph nodes
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1. Respond primarily to antigens entering the body through skin and subcutaneous tissues
2. Encapsulated, ovoid clusters of lymphatic tissue 3. Found throughout the body 5. Constant circulation of lymphocytes between nodes, tissues, lymph, blood |
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Function of lymph nodes
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a. Survey of lymph by macrophages
b. Storage and activation of B and T cells c. Antibody production |
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Cortex of lymph nodes
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a. B cells
i. Primary follicles→ naïve B cells (never come in contact with antigen) ii. Secondary follicles → germinal centers iii. No/few secondary follicles in B cell deficiencies |
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Paracortex of lymph nodes
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a. Poorly developed in DiGeorge syndrome
b. Enlarged during cellular immune responses |
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Medulla of lymph nodes
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a. Plasma cells and macrophages
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Spleen
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1. Responds to blood-borne antigens
2. Major site of antibody synthesis 3. Asplenic persons are susceptible to encapsulated bacteria |
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Types of encapsulated bacteria
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a. Streptococcus pneumoniae
b. Haemophilus influenze c. Neisseria meningitides d. Salmonella e. SHINS mnemonic |
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Splenic white pulp
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a. PALS: T cells surround a central arteriole
b. B cells located between the PALS and marginal sinus c. Primary and secondary B cell follicles d. Lymphocyte-rich |
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Splenic red pulp
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a. Primary function → hemocatheresis
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Mucosa-associated lymphoid tissue (MALT)
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antigens entering through mucosal surfaces
2. B cells produce secretory IgA 3. >50% of body’s lymphoid tissue 4. GALT 5. BALT 6. GU-ALT |
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Peyer's patches of small intestine
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a. M cells→ epithelial cells that mediate transcytosis of antigens from lumen to subepithelial T cells
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Location of MALT
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8. Tonsils, adenoids, appendix
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Lymphocyte homing
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1. Tendency for certain lymphocytes to localize to particular anatomical sites
ii. Lymphocytes leave the bloodstream and enter the tissues by extravasation/diapedesis |
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Homing regulation molecules
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a. → Chemokines
b. → Chemokine receptors c. → Adhesion molecules |
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Integrins
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a. a and beta proein chains
b. LFA-1 (CD11/CD18) |
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Immunoglobulin superfamily members
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a. Globular proteins or glycoproteins
b. ICAM-1 |
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Selectins
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a. Lectins with specificity for carbohydrates
b. E-selectin |
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Carbohydrates
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a. Ligands for selectins
b. Sialyl Lewis X |
