Immunology - MHC Class 1 and 2 Flashcards

Study Notes

Major Histocompatibility Complex (MHC)

Family of genes encoding cell surface proteins known as MHC molecules.
MHC class I and II play vital roles in antigen presentation to T cells.
Essential for distinguishing between human and foreign cells.
Foreign MHC molecules in transplanted tissue can trigger T cell responses, potentially resulting in transplant rejection.

Human Leukocyte Antigen (HLA)

Molecules present on all nucleated body cells, aiding in the identification of foreign cells by the immune system.
Inherited from parents and crucial for assessing compatibility in organ transplantation (e.g., kidneys, pancreases).
Major HLA antigen groups include HLA-A, HLA-B, and HLA-DR.

Three Classes of Membrane Markers (MHC)

MHC is categorized into three classes: Class I, Class II, and Class III.

MHC Class 1

Present on most nucleated cells, they help differentiate healthy cells from infected ones.
Healthy cells present self-antigens on MHC class I, aiding leukocytes in recognizing these cells and leaving them undisturbed.

MHC 1 Binding for Healthy Cell

Healthy cells bind normal peptides (self-antigens) to MHC class I.
Leukocytes recognize these self-antigens, resulting in the preservation of healthy cells.

MHC 2 Binding for Infected Cell

In infected cells, viral peptides are produced and displayed on MHC class I.
Leukocytes identify these antigens, marking the cells for degradation.

MHC Class 1 Structure

Composed of alpha 1, alpha 2, alpha 3 (linked to the cell membrane) and beta 2.
Features a large "cleft" for binding self-antigens.

MHC Class 2

Exclusively found on specific immune cells such as B lymphocytes, macrophages, dendritic cells, and some T lymphocytes.
Crucial for communication among immune cells.

MHC Class 2 Binding

Macrophages engulf foreign cells and release antigens.
The antigen is positioned in the MHC class II complex to attract Helper T Cells via interleukin-1.
Helper T Cells bind to the MHC class II and antigen, releasing interleukin-2 to recruit B-Lymphocytes and T-Lymphocytes.
This process enables differentiation into plasma cells, cytotoxic cells, and memory cells.

MHC Class 2 Structure

Similar to Class I but includes beta 1 and beta 2 (attached to the membrane), along with alpha 1 and alpha 2 (also attached to the membrane) peptides.

Description

Explore the Major Histocompatibility Complex (MHC) with these flashcards focusing on Class I and Class II molecules. Understand their critical role in antigen presentation and how they influence T cell responses, particularly in the context of tissue transplantation. Enhance your knowledge of immunological concepts and their importance in the immune system.