A histological and immunohistochemical study was made on
schistosomula, associated inflammatory reactions and deposition of
schistosomal antigens in lung tissues of normal mice and mice immunized will;
partially purified soluble egg antigen (SEA) of molecular weight 100-137k
dalions. Schistosomula and inflammatory foci were counted by histologic
scoring in 20 lung sections/mouse taken at intervals of 30 p apart. Results
showed that in normal mice, schistosomula number reached their peak on day 7
post infection then rapidly decreased until they were barely detectable on day
25. In immunized mice, they reached their peak on day 9 then gradually
decreased so as many worms were still retained in the lungs on day 25. Mat is,
the rate of elimination of lung schistosomula was much slower in immunized
mice. The pulmonary cellular reaction in immunized mice was evident as early
as day 7 and from day 9 onwords, mononuclear infiltrations were increasing.
Inflammatory foci appeared earlier (day 7) and significantly increased on
subsequent days. The reaction, therefore, was anamnestic, most probably of
delayed type hypersensitivity (DM) response. In normal mice, the reaction was
mild and started late. Schistosomal antigen deposition in lung tissues was
markedly augmented in immunized mice with inure consequent stimulation of
the immune response. So, this study indicates that immunization with this type of
antigen causes augmentative lung resistance against challenge infection as it
was effective in blocking migration of schistosomula by stimulating
inflammation in lung tissues and so may be of value in vaccination studies
against schisto.s'omiasis. However, it should be necessary to guard against
excessive inflammation and pulmonary fibrosis. |
