MHC II

Definition

MHC II (Major Histocompatibility Complex class II) are proteins found on the surface of certain immune cells that present antigens to T-helper cells. They play a crucial role in initiating the immune response by displaying foreign peptides to T cells.

5 Must Know Facts For Your Next Test

1. MHC II molecules are primarily expressed on antigen-presenting cells such as dendritic cells, macrophages, and B cells.
2. They present exogenous antigens, which are typically derived from extracellular pathogens like bacteria.
3. The interaction between MHC II molecules and CD4+ T-helper cells is essential for the activation of these T cells.
4. Peptides presented by MHC II molecules are usually 13-18 amino acids long.
5. MHC II gene expression is regulated by cytokines such as interferon-gamma (IFN-γ).

Review Questions

Related terms

Antigen-Presenting Cells (APCs):

Cells that display antigens on their surface using MHC molecules to activate T lymphocytes.

CD4+ T-helper Cells: A subset of T lymphocytes that recognize antigens presented by MHC II molecules and help orchestrate the immune response.

Exogenous Antigens: Antigens that originate outside the host cell and are typically taken up by APCs through phagocytosis or endocytosis.