Quantitation of B and T lymphocytes in guinea pigs with evidence for a release of both cell types from the spleen into the blood.

B and T lymphocytes were quantitated in lymphoid organs and in blood of young normal guinea pigs by the use of EAC rosettes and rabbit erythrocyte (RE) rosettes as markers. Special attention was focused on the release of B and T cells from the spleen, estimated from the difference between the content of B and T cells in splenic efferent and afferent blood. The following frequencies of resette-forming cells (RFC) were found. Thymus: 0.3% EAC- and 88% RE-RFC; spleen: 44% EAC- and 46% RE-RFC; lymph nodes: 13% EAC- and 39% RE-RFC; arterial blood: 13% EAC- and 42% RE-RFC, and bone marrow: 2% EAC- and 7% RE-RFC. A fairly large number of cells in the lymph nodes and blood could not be identified by any of the two markers. Some possible explanations for this are discussed. The content of both EAC- and RE-RFC in splenic efferent blood significantly exceeded that in the afferent blood, indicating a release of both B and T cells from the spleen into the blood. The possibility of a release of a third type of mononuclear cell cannot be excluded from the present results.