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. 2021 Jan 6;11(1):63. doi: 10.3390/biom11010063

Figure 2.

Figure 2

Conventional antibodies and nanobodies. (A) Immunoglobulin-G (IgG) with 2 heavy (H) and 2 light (L) chains. The L chain comprises 1 variable (VL) and 1 conserved (CL) domain, whereas the H chain contains 1 variable (VH) and 3 constant (CH1, CH2 and CH3) domains. The paired VH and VL domains form the variable fragment (Fv) and bind to the antigen. The L chain and the first half of the H chain (VH and CH1) are known as the antigen binding fragment (Fab). The CH2 and CH3 domains of the 2 H chains form the crystallizable fragment (Fc). (B) Heavy chain-only antibodies (HCAbs) are smaller than conventional antibodies. They are devoid of L chains and the H chain lacks a CH1 domain. HCAbs recognize antigens via the variable domain of the H chain of HCAbs (VHH), also known as a nanobody.