How many subgroups exist within the MHC family?

The major histocompatibility complex (MHC) is crucial in immune response, and it is categorized into different subgroups based on function and structure. The correct answer reflects the presence of three primary subgroups within the MHC family: MHC class I, MHC class II, and MHC class III.

MHC class I molecules primarily present intracellular antigens to CD8+ cytotoxic T cells, playing a vital role in the recognition and destruction of infected or malignant cells. MHC class II molecules, on the other hand, present extracellular antigens to CD4+ helper T cells, which are essential for orchestrating the immune response. MHC class III includes various molecules that are involved in the immune response but are not restricted to the same pathways as the class I and II molecules.

Understanding these three subgroups is essential for grasping how the immune system distinguishes between self and non-self and mounts appropriate responses to pathogens. MHC diversity and the roles of its classes are fundamental concepts in immunology and molecular biology.