Marion M. Zatz

The distribution of chromium 51-labelled lymphoid cells in the mouse: A survey of anatomical compartments

Abstract 51Cr-labeled lymphoid cells derived from lymph node, peripheral blood, spleen, Peyers patches, and thymus migrate distinctively into syngeneic recipients. Each compartment segregates in different ratios into lymph node, spleen, and liver-seeking components. The lymph node-seeking population is believed to represent a pure component of recirculating lymphocytes, while the spleen-seeking population represents recirculating and nonrecirculating cells, as well as hematopoietic precursors. It is proposed that the liver component probably consists of macrophages and dead and dying cells. The functional cell types which these subpopulations may represent is discussed, and quantitive estimations of the size of the recirculating and nonrecirculating compartmental components are made.

Spontaneous AKR lymphoma with T and B-cell characteristics

THE existence of surface immunoglobulin on thymus-derived cells (T cells) has been difficult to demonstrate and is still controversial1–6. Therefore the presence of easily detectable surface immunoglobulin (sIg) is considered to be a reliable marker for lymphoid cells of bone marrow origin (B cells)7. To our knowledge no cell line has been reported to bear both easily detectable sIg (that is, by immunofluorescent staining) and T-cell markers, although two murine T-cell lines have been reported to bear small amounts of sIg detectable only by extremely sensitive methods (2,8). We now report the existence of a murine lymphoma line with both T and B-cell characteristics by the criteria of easily detectable sIg, presence of Thy1.1 (θ AKR) antigen9, and mitogen responsiveness.

Enhancement of murine thymocyte cytotoxic T cell responses by thymosin

Incubation of murine thymocytes with thymosin Fraction 5 (F5) results in a twofold enhancement of the cytotoxic T lymphocyte response (CTL). The assay exhibits requirements for optimal concentrations of thymosin (100 micrograms/ml) and optimal responder/stimulator ratios. Enhancement of CTL activity can be demonstrated in several responder/stimulator strain combinations. The data indicate that thymosin F5 acts via the responder thymocyte population rather than the stimulator cells, since comparable effects were obtained using nude spleen stimulator cells devoid of mature T cells. This system provides a useful bioassay for identifying the component peptides of thymosin F5 which promote thymocyte differentiation and/or maturation and for elucidating the mechanisms of action of the biologically active thymosin peptides.

On the mode of action of thymosin

Abstract Thymosin was administered to CBA mice which had been depleted of recirculating small lymphocytes by combining ALS and thymectomy or through lethal irradiation of thymectomised mice reconstituted with syngeneic bone marrow. The population of recirculating small lymphocytes was monitored by determining the numbers of “lymph node localising” cells in the lymphoid organs of treated animals. In no case was there any evidence that thymosin treatment accelerated the recovery of recirculating lymphocytes. Moreover, it was not possible to show that bone marrow cells incubated with thymosin acquired theta-positivity. We conclude that thymosin does not act by augmenting the production of mature recirculating small lymphocytes.