Immunoregulation in the common marmoset, Calithrix jaccus: functional properties of T and B lymphocytes and their response to human interleukins 2 and 4.

Non-human primates have been used to study immune function to a much lesser extent than readily available strains of inbred rodents. Nevertheless, in situations where it might be desirable, but impossible, to study human immune responses in vivo, lower primates could provide an acceptable alternative. In order to extent the knowledge of T- and B-lymphocyte function in lower primates, the common marmoset Callithrix jaccus was used as an experimental model. The functional similarities between this species and humans at the level of T-B co-operation in the antibody response were examined, and xenoreactive T-lymphocyte clones were obtained from marmoset spleen cells using Epstein-Barr virus (EBV)-transformed human B cells as stimulators. These clones could act as helper cells when co-cultured with human B lymphocytes, inducing the secretion of both IgM and IgG. Lymphokine production by mitogen-stimulated marmoset T-cell clones was also examined. Interleukins (IL) 2 and 4 activities were detected in clone supernatants using bioassays and interferon-gamma (IFN-gamma) was detected using a solid-phase ELISA system. However, SDS-PAGE analysis of biosynthetically labelled marmoset and human T-cell clone supernatant proteins revealed major differences between the soluble T-cell products of the two species. The proliferative responses of marmoset T and B cells to recombinant human IL-2 and IL-4 were also examined. Stimulation of [3H]thymidine uptake was detected in both T cell- and anti-IgM-stimulated B-cell cultures with both of the lymphokines. These results suggests that the key components of the antibody response are functionally conserved between lower primates and man and that the common marmoset may be useful as an in vivo model of immune function, particularly with regard to the role of interleukins such as IL-2 and IL-4.