Selective depression of thymus-independent anti-DNP antibody responses induced by adult but not neonatal splenectomy.

The effect of splenectomy was assessed on rats' capacity to respond to 2,4-dinitrophenol (DNP) conjugated to spider crab haemocyanin (MSH) or hydroxyethyl starch (HES). The response to DNP-HES was profoundly suppressed in all immunoglobulin classes and subclasses by adult splenectomy. This loss of responsiveness increased with time after removal of the spleen. By contrast no significant effect on the anti-DNP-MSH response was caused by splenectomy. Experiments in congenitally athymic rats confirmed the thymus dependency of anti-DNP antibody responses of all classes and subclasses induced by DNP-MSH. DNP-HES responses, however, were elevated in athymic animals. The effect of adult splenectomy in these animals was considerably less than that produced in euthymic rats. Neonatal splenectomy in euthymic rats only resulted in minor impairment of these rats' capacity to respond to DNP-HES as adults, indicating the ability of rats to compensate after neonatal but not adult splenectomy. These data are taken to show that the spleen plays an important role in responses against this thymus-independent type II antigen which is only partially replaceable by other compartments of the immune system.