Autoantibodies against rat prostate antigens. Association of specific IGG2b and IGG2c with the DTH response

Although autoimmune response against most tissues in the body has been extensively described, very little is known about autoimmune response against prostate antigens either in humans or animals. In this work we studied the autoimmune response elicited against rat prostate (RP) in Wistar rats immunized with a chemically modified extract of syngeneic male sex accessory glands (MRAG). We observed that one immunization was enough for the induction of positive delayed-type hypersensitivity test (DTH), which was higher on day 15 than on day 30. It was also enough to induce IgG autoantibodies to RP although a second injection was necessary to obtain a more frequent occurrence and a greater reactivity. The autoantibodies against RP were directed mainly to the cytosolic fraction and reacted at least with two molecules of 43 and 20 KD. Sera obtained on days 30 and 45 showed presence of specific IgG, IgA and IgM. Specific IgG2b and IgG2c were found on both days. On day 30 none of the sera presented IgG2a anti-RP, while on day 45 only 38% of the sera were considered positive for this isotype. No IgG1 anti-RP was detected in any serum of either bleeding. Direct immunofluorescence staining showed intense immunofluorescence in prostate epithelium, mainly in the apical zone of the gland, in animals that had received two immunizations with MRAG-CFA. No positive staining was seen in prostates obtained on day 30 after just one immunization, in sections of normal prostates or in sections of other rat organs. Our data indicate that the main isotypes involved in this autoimmune phenomenon are IgG2b and IgG2c. A strong association between the cellular autoimmune response measured by the DTH response and the IgG2b and IgG2c isotype was found at early stages of the disease. Since the DTH response and the IgG2b isotype have been previously associated with Th1-like activity in rats, our results suggest that Th1-like cells could be playing an active role in early stages of this disease.