To isolate a stable tumor cell line source of Interleukin 2 (IL-2 formerly referred to as T cell growth factor), over 40 murine leukemia and lymphoma cells as well as 9 clonal helper and killer IL-2-driven T cell lines were screened for both constitutive and mitogen-stimulated IL-2 production. A radiation-induced splenic lymphoma from the B10.BR mouse, the LBRM-33 cell line, could be stimulated to produce over 1000 units/ml of IL-2 after 24 hr exposure to T cell mitogens. Peak IL-2 activity was found in supernatants harvested from 24-hr cultures of either 1% PHA or 20 micrograms/ml Con A-stimulated LBRM-33 cells (10(6) cells/ml). IL-2 production observed in both serum-free and serum-containing cultures represented between 1000 and 5000 times the quantity of IL-2 produced in conventional cultures of mitogen-activated rat or mouse spleen cells. Peak IL-2 production by LBRM-33 cultures (stimulated at either optimal Con A or PHA concentrations or co-stimulated with suboptimal amounts of mitogen and phorbol myristate acetate) was consistently accompanied by LBRM-33 cell death. Phenotypic characterization of the producer cell revealed LBRM-33 cells to be Thy 1+, Ly 1+, Ly 2+, Ly 3+, Qa 2-3+, Qa 3.2+, Qat 4+, and Ly 5+. These studies provide further evidence that IL-2 is a T cell product and establish a source of IL-2 that will be a valuable reagent for the isolation and further molecular characterization of this immunoregulatory molecule.

Lymphocytes are a diverse group of cells. One aspect of this diversity is the division of lymphocytes into various classes and subclasses; for example, lymphocytes are classified as T cells or B cells, and each of these classes may be further subdivided into subclasses of cells with distinguishing characteristics and functions. Since the ultimate origin of lymphocytes is a common precursor cell type, lymphocyte differentiation may be evisaged as a progressively branching genealogical tree. Thus diversity may be related to progression down the genealogical tree (sequential differentiative changes) or to occupancy of parallel branches of development. In this respect, the problem of the origin of lymphocyte diversity resembles in microcosm the larger problem of cellular diversity of the metazoan organism, in which a single cell, the zygote, gives rise to the multiple differentiated cell types of the adult organism. However, superimposed on this general problem, the discipline of immunology has...

IT is generally considered that the Y chromosome is necessary for the development of the mammalian testis and the consequent male phenotype. Exceptions occasionally occur in man and other animals, where a male phenotype is associated with an apparently normal female karyotype. In some instances it has been possible to show that such “sex reversal” has an autosomal genetic basis. Although this might imply that the Y chromosome is not a prerequisite of maleness, it has not been excluded that a small male-determining region of the Y may have been translocated to an autosome without producing a recognisable karyotypic change1 (reviewed in ref. 2). The best studied case of male development with an apparently female karyotype is provided by the Sxr mutant in the mouse. This autosomal dominant condition causes both XX and XO mice to develop as males, although germ cells are absent in Sxr,XX animals and spermatogenesis is impaired in Sxr,XO mice. Sxr,XY males have a slightly reduced testis size but are usually fertile. Cytological scrutiny of mitotic and meiotic chromosomes (including chromosome banding) has revealed no evidence for a Y–autosome translocation, although a small translocation undetectable by the methods used cannot be ruled out (reviewed in ref. 2). This situation can now be investigated using serological methods for detecting H–Y (histocompatibility–Y) antigen on the surface of mouse sperm3 and male epidermal cells4. These techniques have provided further evidence that expression of this antigen is governed by a gene (or genes) on the Y chromosome even in the absence of the normal male phenotype5. Thus, serological demonstration of H–Y antigen offers a non-karyological criterion for the presence of a translocated portion of the Y in Sxr,XX males, because their cells should express H–Y if Sxr is a translocation involving the H–Y genetic determinant. We report here that Sxr,XX males express H–Y to a degree that may be the same or slightly lower than that of normal males, and that their Sxr,XY siblings seem to have near-normal levels of H–Y. The simplest explanation is that male-determining and H–Y-determining portions of the Y chromosome are present in the animals carrying Sxr.

THE X-linked testicular feminisation mutant (Tfm) in the mouse produces chromosomally male animals, XTfm/Y, with small testes but no other internal reproductive organs, and with female external genitalia1. This condition results fromfailure of target tissues to respond to testosterone, so that all characters of maleness that are testosterone-dependent are absent in males2–4.

A polypeptide of 8500 molecular weight is described that induces the differentiation of T (thymus-derived) cell and B (bone-marrow-derived) cell immunocytes in vitro, apparently via beta-adrenergic receptors and adenylate cyclase activation. This polypeptide shows a high degree of evolutionary conservation, exhibiting close structural, functional, and immunological similarity when isolated from such diverse origins as cells of mammals and higher plants. This polypeptide was detected in animal cells, yeast, bacteria, and higher plants, and so may well be a universal constituent of living cells.

Single cells were prepared from mouse tail epidermis by a method which gives high viability counts and so permits their use in cytotoxicity tests. According to tests with standard alloantisera, the antigen phenotype of mouse epidermal cells is H-2(+)theta(+)Sk(+)H-Y(+)TL(-)Ly-A(-)Ly-B,C(-)PC(-). The skin differentiation alloantigen Sk, which is responsible for homograft reactions directed selectively against skin, is expressed also on brain, but not on other cell types; it is present on the transplanted neuroblastoma C1300. Cytotoxicity tests with epidermal cells of H-2 congenic mouse stocks confirm that the Sk locus is not closely linked to H-2. The lymphoid cell differentiation antigen theta also is present on both epidermal cells and brain. Mice frequently retain theta-incompatible or Sk-incompatible skin grafts although they have formed substantial titers of theta or Sk antibody in response to grafting. Male (H-Y) antigen is demonstrable on epidermal cells by cytotoxicity tests with H-Y antibody, as it is also on one other type of cell, spermatozoa.

WHEN inbred mice are grafted with skin from inbred donors that differ from the recipients only by a single minor histocompatibility antigen, it is commonly observed that some recipients will retain their skin grafts while others will reject them. This is true of incompatibility for H-Y antigen, which is responsible for the rejection of male grafts by otherwise histocompatible inbred females of the same inbred strain1. Thus in the DBA/2 (DBA) strain, male-to-female skin grafts are rejected by only some recipients; in the C57BL (B6) strain, females always reject male skin; and C3H/An (C3H) females usually accept male skin grafts indefinitely.

WE have recently overcome certain technical difficulties in applying the cytotoxicity test to mouse spermatozoa and have been able to show directly that H-2 antigens are expressed on these cells1, thus confirming less direct evidence leading to the same conclusion2. We have since applied the cytotoxicity test to sperm with antisera directed against a number of other systems of mouse alloantigens, TL3, θ4, Ly-A5 and Ly-B5, but none of these has given a positive reaction with sperm. This is not surprising because these are all “differentiation antigens”6 expressed primarily on lymphoid cells. Another antigenic system which distinguishes one mouse from another is H-Y. The H-Y antigen is carried by male cells only and is responsible for the rejection of male tissues by females of the same inbred strain7.