IMMUNOLOGY

Detailed explanation-1: -Antigens and dendritic cells (DCs) reach the draining lymph node through afferent lymphatic vessels; they must then enter the lymph node and migrate deep into it to activate T cells. Lymph nodes are enclosed in a collagen-rich capsule, which is underlined with lymphatic endothelial cells forming the subcapsular sinus.

Detailed explanation-2: -According to our model, T cells were the first lymphocytes to acquire variable-diversity-joining-type receptors, and the thymus was the first lymphoid organ to evolve in vertebrates to deal with potentially autoreactive, somatically diversified T cell receptors.

Detailed explanation-3: -The lymph node is the first place that immune cells encounter blood-borne antigens. The spleen is classically considered an organ that “filters” antigens from blood. The lymph node receives antigens principally from the afferent lymphatics.