B lymphocytes in the guinea pig thymus are specifically localized in the central area

Since the central area is an integral part of the guinea pig thymus, the cells in this area were compared with those in the thymic cortex and medulla in cryostat-sections by using methods for demonstration of E-, EA-, EAC-adherence and surface membrane immunoglobulins. In the extra cortical central area (ECCA) 15 to 25% of the lymphocytes showed EAC-adherence and 5 to 10% appeared to bear surface membrane immunoglobulins (SIg). In the lymph sinuses up to 70% of the lymphocytes were EAC- and SIg-positive. A small amount of EAC-adhering cells was present in the medulla of the central area. Cortical lymphocytes were EAC- and SIg-negative. From these results we conclude that in the guinea pig thymus B lymphocytes are specifically localized in the central area.