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8 Cards in this Set

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what's the region of human MHC called? what are the subtypes?
major histocompatability complex in humans is on Csome 6 and is called HLA - human leukocyte antigen.

There's Type 1 - which comes in A, B and C.

There's Type 2 - this comes in DP, DQ, and DR.

There's also a random type III involved in complement, but we don't have to know too much about it.
so, we know there are two HLA's that are important in people. what do they look like?
remember that type 1 can be A B or C, type 2 is DR, DP, and DQ.

type 1 is three alpha chains bonded to a B2-microglobulin

Type 2 is an alpha and a beta chain.
what cells do we find MHC class I and II on?
MHC I is on all cells with a nucleus - so noteable exceptions would be RBC's, as they don't have a nucleus.

MHC II is on professional antigen presenting cells - including B cells macrophages, and dendridic cells (probably not follicular dendridic cells, but definitely interdigitating dendridic cells).
MHC 1 and MHC2 - what cells are presented to with these?
remember that MHC1 is on all cells and MHC2 is on professional APC's. Also recall that MHC1 comes in ABC and MHC2 comes in DR, DQ, and DP.

MHC1 cells present to CD8 cytotoxic T cells, which is a good thing because all cells need killing when they get infected with something bad.

MHC2 cells present to CD4 cells - this is good because professional APC's, which are monitoring the immune system, probably want to talk to the cell in charge of controlling the immune response.
talk about some functional differences between the way MHC1 and MHC2 cells package MHC and antigen together.
Remember that MHC1 cells are going to present to CD8 cells. the presented antigen is generally going to be viral or self in nature.

MHC2 is going to present to CD4 cells, and it's usually going to be an exogenous antigen that'll turn on the immune response. it's also on professional APC's.

Big difference is the clip present in MHCII cells. MHCII is synthesized and "clipped", floating aorund, waiting for antigen. has to be de-clipped by HLA-DM, then it encounters antigen, gets presented to Cd4 cells.

If HLA1, usually get synthesis of the HLA and then the viral/self antigen packaged along with it in the ER and presented. No clip.
talk about the two kinds of T helper cells and what usually presents to them:
remember that CD4 cells are going to get presented to by MHCII-bearing professional cells.

It's divided into B cells, and everything else (macs, dendridic cells, etc).

B cells present to TH2, macs and dendridic cells to TH1.
What do the CD4 and CD8 molecules physically do?
they stabilize the binding of a T cell to an MHC + antibody complex on a cell (if CD8, likely a viral partical on a noraml cell, if CD4, likely exogenous pathogen on professional phagocyte).

note they bind to a particular genetic site on the HLA - this is called HLA restriction. You need to have CD4 and CD8 molecules that will physically fit with your own HLA, or it won't work.
more in the next lecture, but imagine presentation to T cells by and MHC/antigen complex. what has to happen, generally?
need a "First signal" - this is the MHC-ag complex binding with the TCR, and CD4 or CD8 stabilizing the reaction.

Also need a "second signal" - this comes from costimulatory molecules present on the T cell that have to bind the presenter.