The possible role of the thymus in autoimmune disease was studied by comparing the effects of neonatal thymectomy on New Zealand Black (NZB) mice (which develop a Coombs positive haemolytic anaemia) and on C3H/Bi, F1 (C57BL × C3H/Bi), C57BL and TO mice.
The neonatally thymectomized NZB mice, in common with those of other strains, showed lethal wasting, a lymphocyte deficit in their lymphoid organs and blood, their packed cell volume was reduced and some had liver lesions associated with the hepatotrophic virus MHV-1. As in C3H/Bi and hybrid mice, thymectomy had little effect on the levels of immunoglobulins (IgG, IgA, IgM) present in their sera.
Removing the thymus from NZB mice did not prevent and could precipitate Coombs positive reactions; thymectomized mice of the other strains were Coombs negative. Although germinal centres develop and plasma cells occur in the lymphoid organs of most thymectomized mice, the striking feature of the NZB mice was the large number, size and activity of the germinal centres that persisted after thymectomy.