American Board of Surgery Qualifying Exam (ABS QE) Practice Test

Which cells primarily respond to MHC and HLA molecules?

1. B cells

2. Neutrophils

3. T cells

4. Antigen-presenting cells

The correct answer is: T cells

T cells primarily respond to MHC (Major Histocompatibility Complex) and HLA (Human Leukocyte Antigen) molecules because their activation is dependent on the presentation of peptides bound to these molecules. MHC molecules are crucial for the immune response, as they display antigens from pathogens on the surface of cells. There are two main classes of MHC molecules: Class I and Class II. Class I MHC molecules present endogenous antigens to CD8+ cytotoxic T cells, which can then recognize and destroy infected or cancerous cells. Class II MHC molecules present exogenous antigens to CD4+ helper T cells, which play a pivotal role in orchestrating the adaptive immune response by helping other immune cells. The interaction between T cell receptors (TCR) on T cells and the peptide-MHC complex is essential for T cell activation and subsequent immune responses, making T cells the primary responders to MHC and HLA molecules in the body.