Lack of heterogeneity in anti-hapten antibodies of a phylogenetically primitive shark

Abstract

Individual mammals have the capacity to express at least one million distinct antigen binding specificities, implying a high degree of structural heterogeneity in the variable heavy and light chain (V_H and V_L) portions of the antibody molecules. Studies of higher vertebrate species suggest that this heterogeneity is created both through a sizeable repertoire of germ-line V_H and V_L genes¹ and through random rearrangements of V and joining genes^2–4. Additional somatic mechanisms probably also contribute to the ultimate heterogeneity; one-third of murine plas-macytomas producing λ₁ immunoglobulin carry a somatically mutated Ig1-V gene^5,6. The relative contributions of these various mechanisms to the overall immunoglobulin variability are difficult to evaluate. The production of different antibodies to a defined determinant in different individuals of an inbred mouse strain [for example, (3-iodo-4-hydroxy-5-nitrophenyl) acetyl (NIP) in CBA mice⁷] suggests the involvement of somatic mutations or rearrangement but does not rule out the possibility that each individual CB A mouse expresses only a small random fraction from a large germ-line repertoire of V genes determining different anti-NIP binding sites. The opposite finding, that different individuals produce nearly identical antibodies to a defined determinant, would suggest the presence and expression of a limited number of germ-line genes without somatic alterations. Data presented here suggest that primitive sharks (Heterodontus fransisci)⁸ produce such antibodies to the hapten furyloxazolone.