How does involvement of MHC 1 and 2 help immune system?

MHC (Major Histocompatibility Complex) molecules play a critical role in the immune system's ability to distinguish between "self" and "non-self" and help mount appropriate immune responses against foreign pathogens or transformed cells. Here's how MHC class I and MHC class II involvement assists the immune system:

MHC Class I Involvement:

1. Cytotoxic T Cell Activation: MHC class I molecules are expressed on the surface of all nucleated cells in the body. They bind to peptides derived from intracellular proteins, including viral proteins or proteins from bacteria that have infected the cell.

2. Recognition by Cytotoxic T Cells: Cytotoxic T cells (CD8+ T cells) are a type of immune cell that can eliminate infected or cancerous cells. They have receptors that specifically recognize MHC class I molecules complexed with antigenic peptides.

3. Cell Lysis: Upon recognition of the MHC class I-peptide complex, cytotoxic T cells become activated and release cytotoxic molecules like perforin and granzymes. These molecules create pores in the target cell's membrane, leading to cell lysis and destruction of the infected or cancerous cell.

MHC Class II Involvement:

1. Antigen Presentation to Helper T Cells: MHC class II molecules are mainly expressed on professional antigen-presenting cells (APCs) such as macrophages, dendritic cells, and B cells. They bind to and present peptides derived from extracellular pathogens or proteins internalized by the APC.

2. Recognition by Helper T Cells: Helper T cells (CD4+ T cells) are essential for coordinating immune responses. They have receptors that specifically recognize MHC class II molecules complexed with antigenic peptides.

3. Activation of B Cells and Antibody Production: Upon recognition of the MHC class II-peptide complex, helper T cells become activated and release cytokines that stimulate B cells to differentiate into antibody-producing plasma cells. Antibodies are crucial for neutralizing pathogens and marking them for destruction.

4. Immune Memory Formation: Activated helper T cells can also differentiate into memory T cells, which can provide long-term immunity against the specific pathogen.

Overall, MHC class I and MHC class II involvement is critical for the adaptive immune response. MHC class I allows cytotoxic T cells to recognize and eliminate infected or transformed cells, while MHC class II enables helper T cells to activate B cells and produce antibodies, leading to the destruction of pathogens and long-term immune memory. Both MHC class I and class II molecules are essential for ensuring immune surveillance and pathogen elimination in the body.