AP BIOLOGY

Detailed explanation-1: -Helper T-cells have a receptor on their surface called a CD4 receptor. The CD4 receptor interacts with major histocompatibility complex (MHC) class II molecules. MHC class II molecules sense when there’s an infection or foreign substance in your body.

Detailed explanation-2: -T helper cells recognize viral peptides in association with class II MHC protein, usually on the surface of an antigen-presenting cell (APC). These interactions result in T helper cell activation, proliferation and differentiation, providing the affinity of binding is sufficiently high.

Detailed explanation-3: -T cells have dual specificity, so they recognize both self-major histocompatibility complex molecules (MHC I or MHC II) and peptide antigens displayed by those MHC molecules.

Detailed explanation-4: -Although freshly isolated human peripheral T cells are spherical and immobile, the transition to irregular changing shapes can be triggered by either adhesion to cellular monolayers (Arencibia et al.