Immunity in Filariasis of Experimental Animals

Abstract
Summary An investigation was made of the immune responses produced in three laboratory filarial infections: Dirofilaria repens in dogs, a species of filarial infection in monkeys and Litomosoides carinii in cotton rats. Immune sera with a high titre of complement fixing antibodies were obtained by immunizing rabbits with Dirofilaria immitis antigen. These immune sera and sera from infected animals showed only a slight or no immune reactions in vitro against infective filarial larvae, against adults of L. carinii and against microfilariae. Immune serum had no therapeutic action upon infections by L. carinii. Agglutinins, precipitins and adhesins could not be demonstrated. D. immitis antigen had no prophylactic or therapeutic action upon infections by L. carinii. Weak immediate skin reactions were obtained in dogs infected with D. repens, but not in any of the other animals. A doubtful Prausnitz-Kustner reaction was observed with immune rabbit sera. It is concluded that filarial infections do produce a certain immune response but this is small in extent and difficult to demonstrate. The smallness of the immune response may be correlated with the great success of filarial parasites in adapting themselves to their hosts, and it is a good example of the general principle that the more perfect the adaptation of the parasite, the less is the immune response of the host.

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