Subpopulations of mouse testicular macrophages and their immunoregulatory function

Testicular macrophages (TMf) participate together with Sertoli cells in formation of blood-testis barrier. The present experiments were aimed to test their immunoregulatory functions in vivo and in vitro.

TMf were purified by glass adherence, rosetting with opsonized erythrocytes and fractionation on discontinuous Percoll gradient (over 95% purity). Their antigen-presenting capacity in humoral and cell-mediated responses was tested in vitro (Mishell-Dutton cultures, proliferation assay) and in vivo (induction of contact sensitivity reaction).

TMf represent a heterogeneous cell population. Heavier Percoll fractions produce little transforming growth factor (TGF)-beta and are efficient antigen-presenting cells in humoral and cell-mediated immune responses. Lighter fractions produce high amounts of TGF-beta and are rather tolerogenic than immunogenic. Their immunosuppressive activity can be prevented by treatment of TMf donors with cyclophosphamide or in vitro by anti-TGF-beta monoclonal antibody. In non-separated TMf population the immunosuppressive activity prevails.

Subpopulation of TMf able to trigger specific immune responses is present in the testis but remains under control of other TMf subpopulation which minimizes the risk of development of autoimmune reactions.