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ONCO-FOETAL antigens (OFAs) are operationally defined as immunogenic cell surface components present on various types of malignant and foetal cells, but not present on adult cells1,2. As OFAs also seem to be shed from cell surfaces into blood and other body fluids, there is particular interest in the possible diagnostic value of detection of OFAs such as carcinoembryonic antigen1,2 and α foetoprotein3. In spite of many studies in this latter area, there is little information on either the basic function of OFA components or of their possible role in immune responses to tumours in vivo. Their frequent association with rapidly dividing cell populations suggests a role related to growth and differentiation rather than in the neoplastic process itself. Embryonic exposure of the normal individual to OFAs may induce immunological tolerance to these antigens, thus effectively negating any subsequent potential role of OFAs to act as tumour-associated transplantation antigens capable of eliciting an anti-tumour response in vivo in the host2.

THE cellular transfer of immunoglobulin (Ig) production in mice by various lymphoid cell preparations has been demonstrated previously by the use of allotype congenic mouse strains1,2. Lymphoid cell suspensions from one mouse line are injected intravenously into histocompatible but allotype-different, partner-strain mice without deliberate immunisation, and the resulting Ig production ascertained by donor allotype analysis of the sera taken at various times. We have used this transfer system to determine whether anti-μ, pretreatment of lymphoid cells results in suppression of subsequent IgG production2, and in studies on the radiosensitivity of the B cell series (R.E.A., and N.L.W, unpublished). In analysing the results of Ig transfer in such experiments, it has become evident that the possible role of T cells in either augmenting or suppressing the Ig transfer by B cells must be determined, and here we present evidence that such T cell involvement can be demonstrated to varying degrees.

GENETIC polymorphism of the structural genes encoding the class-specific (heavy) polypeptide chains of the immunoglobulin (Ig) molecules provides a useful set of markers for elucidating the arrangement and expression of these genes. On the basis of various antigenic, physiochemical and biological properties, the immunoglobulins of the mouse have been divided into eight distinct classes, IgM, IgD, IgA, IgG1, IgG2a, IgG2b, IgG3 and IgE, with a specific structural gene determining the heavy chain (H) for each class. Previous studies have documented the existence of a genetic polymorphism for five of these H-chain genes1–3, with all the genes being closely linked constituting a heavy chain chromosome region. The most recent of these loci to be demonstrated (Ig-5, determining the δ chain)3 was detected by the reaction of alloantisera prepared against spleen cells from mice differing in both H–2 and allotype. These sera reacted with B lymphocytes of the appropriate allotype congenic strains, as assessed by either immunofluorescence, or cell surface iodination and polyacrylamide gel electrophoresis (PAGE). As most B lymphocytes express cell surface IgM as well as IgD (refs 4–6), we have further pursued these various approaches to identify Ig allotypes and have found a polymorphism of the heavy chain (μ) of murine IgM, a molecule found in pentameric form (19S) in serum, and in monomeric (8S) form on the surface of lymphocytes. This defines a locus, Ig-6, which encodes the μ chain of most mouse IgM immunoglobulin.

Dissociation of Skin Homograft Tolerance and Donor Type Gamma Globulin Synthesis in Allogeneic Mouse Radiation Chimaeras

TECHNIQUES now exist for obtaining clonal growth in semi-solid agar of mouse neutrophil, macrophage, eosinophil, erythropoietic and megakaryocytic colonies1–5. Previous attempts to obtain colony formation by mouse lymphoid cells, however, were unsuccessful and cultured lymphocytes died very quickly, even in the presence of known lymphocyte mitogens. Mercaptoethanol and related substances have been shown to increase lymphocyte proliferation in liquid cultures6 and colony formation in agar by mouse plasmacytoma cells7. Based on these observations, attempts were made to obtain clonal growth of mouse lymphoid cells in agar medium supplemented with 2-mercaptoethanol.

The study of spontaneous autoimmunity in mouse models affords an opportunity to determine the cellular basis of the immune dysregulation observed in this disease. Recently, a new mouse strain, MRL/Mp-Ipr/Ipr (MRL/l) has been developed which carries an autosomal recessive gene (lpr) that results in massive lymph node enlargement concomitant with the development of several autoantibodies. The interest in this strain lies in the possibility that the defect in T-cell regulation of the immune response is manifested at a different level from that in the NZB mouse. It has been reported that the proliferating population of lymphoid cells in the nodes of these mice are T cells, but that many of them are devoid of Lyt surface antigens. We have accordingly initiated several lines of research with these mice, including quantitative flow cytometry characterization of Lyt antigen expression of cells in the lymph nodes of the mice. In an approach to isolate and study the properties of these cells, we have also established continuous cell lines from the lymph node cells of MRL/l mice, using techniques similar to those used to establish continuous lines of antigen-activated cytotoxic T cells and helper T-cell populations.

IN previous investigations it has been found that the normal development of the bursa of Fabricius in chickens is essential if the bird is to develop fully its potential antibody-forming capacity1–3. In these investigations2,3 the development of the bursa was partially or completely inhibited by the intra-embryonic injection of testosterone propionate. When the inhibition of bursal lymphoid tissue was complete, no antibody production could be detected after challenge at 4–6 weeks of age with 5 different antigens3. Providing the thymus in these chickens was morphologically normal, there was no detectable reduction in splenic lymphoid follicles, peripheral blood lymphocyte-levels, or homograft immunity to solid grafts3. A marked reduction in cells of the plasmacytic series has been observed in the spleens of both hormonally3 and surgically4 bursectomized chickens. As these chickens resembled patients with agammaglobulinaemia5 in their inability to produce circulating antibodies, physicochemical studies on the serum immunoglobulins were commenced and form the basis of this presentation.

ALTHOUGH the events occurring during the induction of an antibody response are not clearly understood, it is evident that antigen must react with some type of receptor which is either free in serum or present at a cell surface. Various experiments1–3 in which labelled antigen is allowed to react in vitro with lymphocytes suggest that a very small proportion of all lymphocytes does in fact have the ability to recognize and bind a given antigen. The specificity of this binding reaction between antigen and lymphocyte was demonstrated in both adoptive transfer experiments4 and in vivo3. Electron microscopic studies indicate that the reactive lymphocytes possess localized receptor sites for antigen on their surface5. Preliminary studies2 showed that pretreatment of these cells with a polyvalent anti-immunoglotaulin serum inhibited antigen binding and suggested that the antigen receptor site involves some type of immunoglobulin molecule. We now report in more detail on the nature of the receptor sites on lymphocytes and suggest that interaction of antigen with these sites is crucial in the induction of the antibody response.

POLYVALENT immunological tolerance of varying degrees to histocompatibility antigens can be induced in non-inbred recipients by the neonatal injection of pooled cells from a wide range of donors. This was demon strated by Hasek and Haskova1 in ducks, Koldovsky2 and Billingham and Silvers3 in rats, and by Lengerova4 in mice. All these workers used the acceptance of skin homografts as the criterion of tolerance.

THE function of the mammalian thymus has recently become a matter of considerable interest in the field of immunology. It is now reasonably clear that the presence of the neonatal thymus is essential if the animal is to develop the capacity to reject homografts. This has been shown by Miller1and by Arnason et al.2, who thymectomized mice and rats respectively within 24 h of birth and demonstrated that a skin homograft placed on the animal several weeks later was either permanently accepted1or showed a prolonged rejection time2. This has lent considerable support to the view, originally proposed by Fichtelius3, that the thymus is a primary organ of lymphocytopoiesis which, during the first week of life, sends out lymphoid cells to colonize other lymphoid organs, and where on appropriate antigenic challenge will be stimulated into immunological activity. However, some recent results from Miller4have indicated that the influence of the thymus on the development of immunological competence may not be purely cellular, but may be of a hormonal nature.

FOR some time we have been studying various manifestations of the reaction induced in chick embryos by the inoculation of leucocytes from normal fowls (the Simonsen phenomenon) with special interest in the production of macroscopic foci on the chorioallantois1. In the course of this work it was observed that if hydrocortisone was added to the inoculum the number of foci was diminished and the embryo showed obviously retarded development.

Immunological Function of Thymus and Bursa of Fabricius: Dissociation of Immunological Responsiveness in Fowls with a Hormonally Arrested Development of Lymphoid Tissues

WHEN blood cells from an adult fowl are inoculated on the chorioallantoic membrane of the 12-day-chick embryo, easily visible opaque foci are produced1,2. This reaction is thought to be similar to the induction of splenomegaly following intravenous inoculation of adult fowl blood into the chick embryo3. The cells in blood responsible for this latter action have been found to be the lymphocytes4. Fowls are typical of the avian family in having a high proportion of circulating large lymphocytes, usually about 10 per cent, and, as autoradiographic investigations5,6 have shown that large lymphocytes and not small can synthesize deoxyribonucleic acid and proliferate, an investigation was made to determine the type of lymphocyte responsible for the induction of lesions on the chorioallantoic membrane. Blood from a group of 25 random fowls was titrated on the chorioallantoic membrane, the number of small and of large lymphocytes in the inoculated blood having been determined. A highly significant correlation (0.1 per cent in Student's t test) of the number of large lymphocytes in the inoculum with the median focal count was demonstrated. The correlation of small lymphocytes with the focal count was not significant (> 5 per cent). In repeated titrations of individual fowls, the focal count was also shown to depend on the number of large lymphocytes in the inoculum and to be quite independent of the number of small lymphocytes.