Question

What is the cell‐mediated immune response? What cell types are involved? What is their role? What is the role of an antigen presenting cell? What type of cells are these? What type of pathogen triggers the cell‐mediated immune response? What are MHC class I, II proteins? What is their function? How do MHC proteins correlate to T cells?

Answer 1

Cell mediated immune response involves the activation of phagocytes, cytotoxic T-lymphocytes and the release of cytokines in response to activation triggered by antigen. T cells are involved in this type of immune response. Antigen-presenting cells present antigens to T cells in association with different classes of MHC leads to activation of either macrophages (which carry out phagocytosis) or cytotoxic T cells ( by releasing cytotoxin granules).

Antigen-presenting cells (APCs) are group of immune cells that process and present antigens so that these antigens can be recognized by T cells and thus mediate cell mediated immunity. Examples of APCs include dendritic cells, macrophages, B cells etc.

Pathogens that trigger cell mediated immune response are virus, fungi, protozoans, cancers, and intracellular bacteria.

MHC molecules are proteins that bind to antigens ( from pathogen) and display them on the cell surface so that the appropriate T-cells can recognize it. MHC is divided into three: class I, class II, and class III. Class I MHC molecules present antigen to cytotoxic T cell , they bind to CD8 adhesion molecule on cytotoxic T cells. Class II MHC molecules present antigen and are recognised by T helper cell. Class II will bind to CD4 adhesion molecules on T helper cell.