IMMUNOLOGICAL AND HISTOLOGICAL STUDY OF T-LYMPHOCYTE AND B-LYMPHOCYTEACTIVITY IN CANINE VISCERAL LEISHMANIASIS

Lymphocyte activity during canine leishmaniosis was studied by histolo gical and immunological methods in experimental and natural infections . Eight dogs were inoculated with 5 X 10(7) promastigotes of Leishmani a infantum, LEM 75, zimodeme MON-1, and maintained for 110 days post-i nfection. Another eight dogs with advanced natural infection were iden tified by parasitological and serological methods. Three techniques we re used: the lymphocyte transformation test (LTT) to study T-cell acti vity, immunofluorescence assay and enzyme-linked immunosorbent assay t o measure antibody production (B-cell activity), and methyl green-pyro nin staining to assess tissue responses of lymphocytes. There was a no ticeable B-cell response, reflected both histologically and immunologi cally. High percentages of activated lymphocytes and plasma cells were evident in lymphoid organs and production of specific antibodies was seen throughout the infection. LTT results showed a T-cell unresponsiv eness during canine leishmaniosis. These same immunohistological featu res were observed, although to different degrees, in both experimental and natural infections.