The IgA system of the guinea pig.

The existence of the IgA system of the guinea pig has been established on the following grounds. 1) An 11S immunoglobulin (guinea pig IgA) has been isolated from milk and has been found to differ from IgM, IgG1 and IgG2. 2) An antiserum against this protein contained antibodies capable of eliciting the classical spur of secretory IgA over serum IgA, enabling to identify both the bound and free form of the secretory component. 3) IgA is a minor immunoglobulin constituent of guinea pig serum but a major immunoglobulin in secretions. 4) The electric charge and molecular size properties (large amounts of dimer) of guinea pig serum IgA were those characteristic for this immunoglobulin in other mammalian sera. 5) The majority of the immunoglobulin-containing cells of the intestinal mucosae of the guinea pig produce IgA, in contrast to IgM and IgG which is mainly found in the immunocytes of the spleen and lymph nodes.