RESTORATION OF THE AGED THYMUS BY CASTRATION: ITS CONSEQUENCES ON AN AUTOIMMUNE RESPONSE

MORÓN, G., MALETTO, B,. PISTORESI-PALENCIA, MC.

Barcelona

Congreso; 12th European Immunology Meeting; 1994

The authors have studied the influence of aging on the autoimmune response in an experimental model of autoimmunity against rat male accessory glands (RAG) induced by injection of a saline extract of chemically modified RAG (MRAG). We found a higher autoimmune response, both cellular and humoral, with a more extensive lesion in the target organ developing more rapidly in old rats when compared with young control animals, Furthermore, we showed a higher difficult to obtain suppression of the autoimmune response in the old animals. Restoration of the young-like thymus architecture by deprivation of testoterone was reported some years ago. We have analyzed the effect of deprivation of testorerone in modulating the autoimmune response of old animals. Male Wistar rats (12-months old) were divided in three groups. Groups A (n:.6) was castrated by surgery and 30 days later was immunized with MRAG-CFA, Group B (n:5) was only immunized with MRAG-CFA and Group C (n:5) were injected with CFA. On day 30 the DTH response and the antibody levels were measured and the rats were sacrificed. The accesory glands and one portion of thymuses were extracted and fixed in p-formaldehyde 4% to histologic approach; the other portion was used to count the percentages of CD4 and CD8 thymocytes by immunofluorescence. We found a larger thymus in aged castrated rats than in non castrated animals. Sections of thymus, stained with H-E, from castrated animals had a better developed cortex and more visible cortical, medullar-junction. The percentages of CD4 cells in the thymus of groups A lower than in group B (p<0,001) as was the same as in group C. Differences in the level of CD8 population were not observed. The cellular response of group A, determined by DTH was diminished in comparison with group B (p<0,01) and the humoral response of group A also was diminished with respect to group B. Whit our system we could establish an improved immune system function, which can control the autoimmune response, and this permit to us to affirm that aged castrated animals have diminished auto immune response, and that this decreased response can be attributed to regeneration of the thymus architecture.