In vitro induction of lymphocyte responsiveness by aStrongylus vulgaris-derived mitogen

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Abstract
Proliferation in vitro of peripheral blood lymphocytes both from horses infected withStrongylus vulgaris and from helminth-free ponies was observed in the presence of extracts of the fourth and fifth stage larvae and adults ofS. vulgaris. In addition,S. vulgaris extracts induced transformation in cultures of peripheral blood lymphocytes from sheep and dogs and in mouse spleen cell cultures. Nylon wool non-adherent, T cell enriched fractions of lymphocytes from both mice and horses were stimulated by theS. vulgaris larval mitogen while no proliferation was observed in cultures containing nylon wool adherent, B cell enriched fractions. Macrophage co-operation appeared not to be necessary forS. vulgaris mitogen-induced transformation of spleen cells. TheS. vulgaris mitogen stimulated a subpopulation of mouse spleen cells different from those responsive to PHA, Con A and LPS. These cells might be T helper cells since B cells were stimulated to proliferate in the presence of both T cells andS. vulgaris larval mitogen. In addition, the supernatant of in vitro cultured larvae ofS. vulgaris induced slight, but significant transformation of equine peripheral blood lymphocytes. Therefore, it is possible that theS. vulgaris mitogen released by both viable parasites and degenerating larvae might induce T cell dependent production of immunoglobulin in vivo and account for the β-globulinaemia, of which IgG(T) is a major component, inS. vulgaris infected horses.