CELL-MEDIATED IMMUNE-RESPONSE AND T-LIKE CELLS IN THYMECTOMIZED ONCORHYNCHUS-MYKISS (WALBAUM) INFECTED WITH OR VACCINATED AGAINST THE PATHOGENIC HEMOFLAGELLATE CRYPTOBIA-SALMOSITICA KATZ, 1951
Sj. Feng et Ptk. Woo, CELL-MEDIATED IMMUNE-RESPONSE AND T-LIKE CELLS IN THYMECTOMIZED ONCORHYNCHUS-MYKISS (WALBAUM) INFECTED WITH OR VACCINATED AGAINST THE PATHOGENIC HEMOFLAGELLATE CRYPTOBIA-SALMOSITICA KATZ, 1951, Parasitology research, 82(7), 1996, pp. 604-611
T-cell-mediated delayed-type hypersensitivity (T-DTH) reaction was det
ected in Cryptobia salmositica-infected intact and thymectomized (2 mo
nths post-thymectomy) Oncorhynchus mykiss (Walbaum). Both groups of fi
sh showed significant induration at the site of C. salmositica antigen
injection at 8, 12 and 16 weeks post-infection. A significant differe
nce was not observed in T-DTH reactions between the thymectomized and
intact (control) infected fish. The total numbers of circulating leuco
cytes detected in infected thymectomized fish were significantly lower
than those found in infected sham-thymectomized fish. The numbers of
T-like cells determined (using alpha-naphthyl acid esterase assay) in
thymectomized fish (9 months post-thymectomy) were similar to those se
en in intact fish prior to and at 4 weeks after vaccination with an av
irulent strain of C. salmositica. At 2 weeks after challenge with the
pathogen the numbers of T-like cells in intact vaccinated fish increas
ed significantly (P < 0.01) and remained high for the duration of the
study (15 weeks). However, in vaccinated thymectomized fish the number
s of T-like cells remained low after parasite challenge. These results
suggest that thymectomy in adult rainbow trout did not lower T-cell-m
ediated delayed-type hypersensitivity; however, it reduced the numbers
of circulating leucocytes and retarded the proliferation of T-like ce
lls after antigenic stimulation.