Our immune system, by and large, does a fine job in protecting us from opportunistic and infectious microbes, potential carcinogens and allergens. It is therefore crucial to understand the organization of the immune network. This article focuses on some important features and key players involved in adaptive immune response. The first part of the article dealt with the humoral immune response mediated mainly by immunoglobulins produced by the B cells. The second part deals with T cells, the Major Histocompatibility Complex (MHC)-encoded molecules, and Recombination Activating Genes (RAG) responsible for generating diverse B-cell receptors (BCR) and T-cell receptors (TCR). With the advent of newer and smarter infectious agents, it is important to understand the working of the immune network as more research in this area may facilitate the development of better protective strategies.