Intraspecies heterogeneity of immunoglobulin alpha-chain constant region genes in rhesus macaques

Immunoglobulin A (IgA) is the major antibody class present in external secr etions and is also an important component of serum immunoglobulins. On muco sal surfaces, IgA represents a first line of defence by neutralizing invadi ng pathogens. The number of IgA constant-region genes (C alpha) present in different mammalian species is variable. Immunoglobulin C alpha genes diffe r mainly in the sequences located in the hinge region. IgA molecules, whose hinge regions are remarkably similar to those of the respective human mole cules, are present in hominoid primates. In this report, we show that two a lleles of a single immunoglobulin C alpha are present in rhesus macaques (M acaca mulatta). In addition, we show that intraspecies immunoglobulin C alp ha allelic polymorphism is very high in this non-human primate species. Spe cifically, five different hinge regions, some of which are proline-rich, we re identified from a total of eight rhesus macaque immunoglobulin C alpha - chains. The five hinge regions were different from those present in hominoi d primates, both in length and in sequence. These results represent the fir st example of high levels of intraspecies immunoglobulin constant-region va riability and suggest that IgAs of variable structure and function may be p resent in rhesus macaques. As rhesus macaques are widely used as animal mod els for the development of vaccines for acquired immune deficiency syndrome (AIDS), the possible presence of structurally and functionally variable Ig A molecules in different animals should be taken into account when designin g experimental strategies to induce mucosal antibody responses to human imm unodeficiency virus (HIV).