T-cell development in the absence of a thymus: the number, the phenotype, and the functional capacity of T lymphocytes in nude mice.
A small but definite proportion of T-lymphocyte-like cells have been reported in nu/nu (nude) mouse spleen despite the congenital absence of a thymus in these animals. We have determined the number and the characteristics of such cells using flow cytometry. The level of T-like cells increased with age. In 4-month-old nu/nu CBA spleen, 14% of all cells expressed some Thy 1 antigen. However, only 4% expressed mature T-cell levels, and only the 2% with the highest Thy 1 also showed a normal distribution of Ly 1 and Ly 2 antigens. These T-like cells were slightly larger than normal nondividing T lymphocytes. We have assessed the total functional capacity of T-like cells in nu/nu CBA spleen using a high-cloning-efficiency limit-dilution culture system. Almost all precursor cells capable of forming clones when stimulated with concanavalin A in the presence of irradiated spleen cells and growth factors, and almost all precursors of those clones that were cytolytic in a lectin-mediated tumor-cell-lysis assay, were within this 2% subpopulation of nu/nu spleen cells with mature T-cell markers. Increased levels of purified interleukin 2 failed to induce further precursor function, indicating that maturation of pre-T cells was not obtained. However the nu/nu spleen cells bearing mature T-cell markers displayed only 10-30% of the cloning efficiency of normal splenic T cells. The majority of nu/nu spleen T-like cells, even within this phenotypically "normal" subset, appeared to be nonfunctional. We conclude that the absence of a thymus leads to qualitative, as well as quantitative, deficiencies in the T-cell population, and various interpretations are discussed.
D000818:Animals; D000950:Antigens, Ly / Q000276:immunology; D002452:Cell Count; D003208:Concanavalin A / Q000494:pharmacology; D005434:Flow Cytometry; D007376:Interleukin-2 / Q000494:pharmacology; D008297:Male; D051379:Mice; D008819:Mice, Nude / Q000502:physiology*; D010641:Phenotype; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology*; D013950:Thymus Gland / Q000502:physiology*
D000950:Antigens, Ly; D007376:Interleukin-2; D003208:Concanavalin A