Figure 1.

The structure of antigen-specific lymphocyte receptors and the generation of diversity. (A, B) The structure of BCR and TCR. The heavy and light chains of antibodies are shown, and they are connected by disulfide bonds (bold blue line); TCR that is across the cell membrane is a heterodimer comprised of αβ chains or γδ chains. The upper part is the variable (V) region composed of V(D)J gene in the figure. The V region is composed of CDR regions and FR domains. CDR1, CDR2, and CDR3 are shown in different colors (yellow, blue, and green, respectively). The lower part (white area) is a constant region that is conservative. The structure of lymphocyte receptors shown here contributes to explaining how immune response occurs. (C) The mechanism of lymphocyte receptors repertoire diversity. During the development of lymphocytes, BCR heavy chains or TCR β(δ) chains suffer from the rearrangement of VDJ genes, while the IgL chain or α(γ) chain lack D gene in the rearrangement. Afterward, the rearranged V-DJ or V-J sequences are linked to the C gene fragments. Finally, two independent chains are assembled into unique receptor proteins. Germline gene V(D)JC undergoes rearrangement and insertion and deletion of nucleotides, resulting in the diversity of the receptor library ¹⁶.