IMMUNOLOGY

Detailed explanation-1: -MHC II molecules are expressed only on the surface of antigen-presenting cells (macrophages, dendritic cells, and B cells).

Detailed explanation-2: -Most cells in the body can present antigen to CD8+ cytotoxic T cells via MHC class I; however, the term “antigen-presenting cell” is often used specifically to describe professional APCs. Such cells express MHC class I and MHC class II molecules and can stimulate CD4+ helper T cells as well as cytotoxic T cells.

Detailed explanation-3: -In contrast to MHC class I molecules, MHC class II molecules have a more restricted distribution pattern, and they are predominantly expressed, under normal conditions, by professional antigen-presenting cells (APC), like B cells, macrophages and dendritic cells.