AP BIOLOGY

Detailed explanation-1: -Classical antigen presenting cells (APCs) are dendritic cells (DCs) and B cells (10). To mount an immune response, APCs must first recognize and bind their target. To do so, APCs express antigen-specific surface receptors including pattern recognition receptors (PRRs).

Detailed explanation-2: -Professional APCs include dendritic cells, macrophages, and B cells, whereas nonprofessional APCs that function in antigen presentation for only brief periods include thymic epithelial cells and vascular endothelial cells.

Detailed explanation-3: -Although dendritic cells are important in presenting antigen, particularly to initiate primary immune responses, macrophages are the professional APC type most prominent in inflammatory sites and specialized for clearing necrotic and apoptotic material.

Detailed explanation-4: -Macrophages and dendritic cells function as antigen-presenting cells (APCs). They present peptide antigens derived from digested bacteria on the major histocompatibility complex class II and activate acquired immunity by activating helper T cells.

Detailed explanation-5: -Helper T cells, killer T cells, and macrophages are the three main kinds of lymphocytes involved in cell-mediated immunity. When a “helper” T cell encounters an antigen-presenting cell in the body, it releases cytokines, which are signaling proteins.