Isolation and partial identification of immunoglobulin from T cells.

Using fowl anti mouse (Fab)2 antibody, a protein has been collected from culture fluid and cell lysates of thymoma cells and stimulated thymocytes. This protein did show an immunoglobulin arc on immunoelectrophoresis against abovementioned antibody and against rabbit anti mouse Ig serum. No precipitation lines have been produced by mono-specific anti-mouse gamma, mu and alpha sera. On reduced PAGE heavy and light chains were present. Mobility of the heavy chain was between mu and gamma chains and its apparent molecular weight was calculated at appr. 65,000 daltons. The light chain mobility corresponded to mouse serum kappa chains.

Direct demonstration of murine thymus-dependent cell surface endogenous immunoglobin.

Antisera raised in mammals to murine immunoglobulin (Ig) do not detect surface Ig on thymus-dependent (T) lymphoma cells as assessed by immunofluorescence analysis. In contrast, chicken antibodies, produced against the (Fab)2 fragment of normal mouse IgG and purified by binding to and elution from IgG-Sepharose 4B, give strong indirect fluorescence with murine T cells and cultured T lymphoma cells. The surface Ig caps, is shed, and reappears, indicating that it is of endogenous origin. Nonlymphoid tumor cells of various myeloid types do not bind this reagent, even though they bear avid Fc receptors. The capacity of chicken antibodies to bind to both bone-marrow-dependent and T cell lymphomas was abolished by adsorption with myeloma-derived kappa chains coupled to Sepharose. The kappa antigenic determinant recognized by the chicken antibodies may thus be different from that seen by mammalian antibodies, and the degree of exposure of Ig on the T lymphoma surface might also affect ease of detectability with these reagents. These data provide direct evidence that T lymphocytes and T lymphoma cells express and synthesize a surface Ig containing determinants that at least 'crossreact with bone-marrow-cell-derived kappa chains.

Ontogeny of myelopoietic precursor cells in the chicken embryo.

The agar culture technique which enables enumeration of myeloid precursor cells was used to establish the time of appearance and further development of these cells in chick embryos. Yolk mesenchyme is the largest producer of precursor cells from day 6 to day 17 of incubation. In circulating blood precursor cells probably from the yolk appear at day 9 and stay at fairly high levels till day 17. Spleen and bone marrow have high percentage of precursor cells from day 10 till hatching, but afterwards rapid fall takes place to normal young adult levels. Thymus contains very few precursor cells during whole period of incubation. Bursa of Fabricius shows a very sharp peak of precursor activity on day 14 and 15 of incubation.