Thymus cell maturation. Studies on the origin of cortisone-resistant thymic lymphocytes

Outer thymic cortical large lymphocytes were labeled by transcapsular administration of tritiated thymidine. By 2-4 days after labeling, small and medium labeled lymphocyte descendants were found throughout the cortex and in the medulla. The labeled cortical lymphocytes undergo pycnosis after parenteral administration of hydrocortisone 24 h previously, but their (labeled) medullary descendants do not. In addition, parenteral administration of hydrocortisone at the time of surface labeling results in the absence of the appearance of labeled medullary descendants.

Structural characteristics of some murine RNA tumor viruses studied by lactoperoxidase iodination

Iodination by the noninvasive enzymatic lactoperoxidase technique has been used to study the enzyme-accessible and enzyme-inaccessible proteins of three oncorna viruses (radiation leukemia virus, Moloney leukemia virus, and mouse mammary tumor virus). The number and relative molecular weight of proteins associated with virion preparations purified on sucrose gradients were characterized by scans of Coomassie blue-stained bands after dodecyl sulfate-polyacrylamide gel electrophoresis. Gel scans from the leukemia viruses are similar, each showing six distinct major protein bands on stained gels. The mammary tumor virus proteins by this analysis are not similar to those of the leukemia viruses. Enzymatic iodination of intact virion preparations led to the solitary labeling of one of the major proteins of each virus-the 80,000-dalton protein of the leukemia viruses and the 52,500-dalton protein of the mammary tumor virus. These are tentatively positioned as surface (enzyme-accessible) moieties in the virions. Disruption of each virus with a nonionic nonionic detergent before enzymatic iodination led to the labeling of the remaining stainable bands. The four lower molecular weight bands of the leukemia viruses are tentatively positioned as internal (enzyme-inaccessible) components.

Lymphoid tissue architecture. Experimental analysis of the origin and distribution of T-cells and B-cells

The distribution of bone marrow-derived cells, thymus-derived cells and tissue-bound immunoglobulin was examined using indirect immunofluorescence. It was demonstrated that primary follicle small lymphocytes are bone-marrow derived in the absence of the thymus, they lack thymus-associated antigens, and bear high concentrations of surface-associated immunoglobulins. Thymus-antigen positive cells make up the majority of, if not all, diffuse cortex lymphocytes, do not bear concentrations of surface immunoglobulin detectable in this system, are found as rare cells in primary follicles, and are present in germinal centres. A mechanism is proposed for the thymus—bone marrow interaction in the immune response.

Immunological memory in mice. 3. Memory to heterologous erythrocytes in both T cell and B cell populations and requirement for T cells in expression of B cell memory. Evidence using immunoglobulin allotype and mouse alloantigen theta markers with congenic mice

Using anti-allotype sera and AKR anti thetaC3H sera, a requirement for two cell types has been demonstrated in the adoptive secondary response of mice to heterologous erythrocytes. The cell types have been designated B cells [precursors of plaque-forming cells (PFC)] and T cells (thymus-influenced cells, not providing precursors of detectable PFC). The in vivo indirect PFC response of spleen cells from primed mice is markedly reduced by in vitro treatment of the cells with a mixture of anti-theta serum and guinea pig serum (Anti theta + GPS). This B cell response is fully restored to control levels by thymus cells from normal mice which do not themselves provide precursors of indirect PFC. Thus memory is carried by the B cell lineage but the expression of this memory is dependent on the presence of a cell population which is sensitive to Anti theta + GPS and which is replaced functionally by unprimed T cells. When assayed for T cell activity, thoracic duct cells from specifically primed mice are better than cells from nonspecifically primed mice in restoring the B cell response of spleen cells from immunized mice. Moreover, the T cell activity of a reconstitutive cell population from primed mice is reduced by incubation with Anti theta + GPS. We conclude that memory to heterologous erythrocyte antigens is carried by the T cell lineage as well as the B cell lineage even though unprimed T cells are sufficient for expression of B cell memory.

Thymus cell migration

THE PRECEDING STUDIES HAVE ESTABLISHED THE FOLLOWING POINTS: Intrathymic labeling of thymic lymphocytes provides an adequate marker system to detect the migration of thymus cells to peripheral lymphoid sites. In the newborn, this comprises a major portion of the total lymphocyte population in lymph nodes and spleen. In the adult, this migration is limited to specific portions of lymph nodes and spleen, i.e., those portions which serve the recirculating pool of small lymphocytes. Kinetic studies of labeling within the adult thymus indicate that large cells give rise to medium and small cells, which then migrate to the specific sites noted above. In the newborn, the kinetic pattern is similar to that of adults, with the single distinction that large cells also migrate, accelerating the tempo of migration in these hosts. The long-term fate and function of thymus cell migrants has not yet been determined.