Screening gene expression libraries for epitopes recognized in Mycobacterium leprae by mouse T cells

Parasite expression libraries have so far been screened with antibodies, DNA probes or T cell clones. Immunity to many parasites, such as Mycobacterium leprae, is largely mediated by T cells, and so the screening of such libraries for T cell epitopes is an important step toward the development of effective vaccines and diagnostic reagents. A new method for screening of lambda gt11 libraries with uncloned T cell populations is presented here, which takes advantage of the fact that the recombinant proteins contain beta-galactosidase as their leader peptide; this allows them to be semipurified by means of anti-beta-galactosidase antibodies coated on the bottom of microtiter plate wells, within which a proliferation assay can then be carried out. Optimum conditions for the assay were determined, using the M. leprae 18-kDa antigen as a test antigen.

Dominant reduced responsiveness controlled by H-2(Kb)Ab. A new pattern evoked by Thy-1 antigen and F liver antigen

In the most frequently used panel of H-2 recombinant strains, B10.A, B10.A(4R), B10.A(5R), and B10, inhibition of the immune response has hitherto mapped to H-2E. Inhibition of the responses to Thy-1 antigen and to F liver protein, as described here, maps in a novel pattern to H-2KbAb, and presumably to H-2Ab. Enhancement of the adoptively transferred anti-Thy-1 response by treatment with CD8-specific antibody suggests, very provisionally, that T cells with suppressive activity mediate the inhibition. The evolution of this new pattern, and of dominant reduced responsiveness in general, is discussed and its relevance to immunological diseases assessed. An enzyme-linked immunosorbent assay (ELISA) for F-specific antibodies is introduced.

Thy-1-specific helper T cells can provide intramolecular help, but can provide intermolecular help only if the phosphatidylinositol anchor of Thy-1 is replaced by a membrane insert

We have investigated the ability of Thy-1 to serve as a helper antigen in delivering intermolecular help. The parental Thy-1 molecule, which is attached to the cell surface via a phosphatidylinositol anchor, failed to deliver intermolecular help for an antibody response to H-2 alloantigens. This failure appears to be due to the phosphatidylinositol anchor since a Thy-1 hybrid construct, which is expressed as a transmembrane cell surface molecule, can serve as helper antigen and deliver intermolecular help.

The evolution of acquired immunity to parasites

Evolutionary pressures exerted by parasites on the immune system, and vice versa, are surveyed from a speculative viewpoint. New information is presented about the possible channelling of suppression by MHC Class II genes in the mouse, where a novel pattern of dominant unresponsiveness mediated by H-2Ab is described. In addition, the hypothesis is advanced that phosphatidyl-inositol anchorage on the surface of parasites may represent a novel evasion mechanism, in which the spread of the immune response by epitope linkage is inhibited by host phospholipase.

An exact comparison between the efficiency of two- and three-cell-type clusters in mediating helper activity

Adoptive transfer of anti-H-2Db-primed B cells combined with anti-minor histocompatibility antigen-primed T cells enables the effect of linked and unlinked alloantigen to be compared. Over an extensive dose range the unlinked antigen proved ineffective. In a previously described, exactly comparable system for assessing the same effect on cytotoxic T cell precursors, low doses of linked antigen had proved approximately equally effective, but high doses of unlinked antigen had proved effective. This contrast supports the hypothesis that whereas T-B collaboration is mediated by two-cell-type clusters, collaboration between T cells requires formation of three-cell-type clusters.

Antigen processing: current issues, exceptional cases (Thy 1 alloantigen, MHC class-II-restricted cytolytic T cells), and implications for vaccine development

A dogmatic view of antigen processing is presented in outline, followed by a survey of unresolved issues in the subject. The activity of Thy 1 as an alloantigen, and allospecific MHC Class-II-restricted cytolytic T cells offer examples of exceptional cases of antigen presentation. Implications for the design of vaccines are drawn.

T cells in transplantation immunity

This paper reviews the following problems in transplantation immunity: (i) short-lived ability to transfer immunity or suppression, in contrast to long-lived immunological memory in the autochthonous animal; (ii) short-lived ability to transfer graft-resistance, in contrast to long-lived ability to transfer helper activity for B-cells; (iii) the response to H-Y, as a system that might solve some outstanding problems in antigen presentation; and (iv) the contrast between live and killed allogeneic cells as immunogens. All of these problems, it is suggested, are amenable to study by modern methods. Students like me were drawn into Peter Medawar's orbit in the 1940s and 1950s by an irresistible mix of intellectual challenge and the glamour of experimental surgery. Much the same was happening elsewhere in the laboratories of Ray Owen, Milan Hasek, George Snell, Burnet, and Florey, and by 1960 the transplantation immunologists could justly claim to have opened up a whole new area of ideas in biology: we had discovered the lymphocyte as the antigen-sensitive cell, and the principles of immunological tolerance; we had revived interest in cellular immunity, and it was we who found the MHC (even if we had little idea of its real meaning). But by 1960 the first wave of success had passed, and the penetration of immunology by molecular biology had begun. Interest in transplantation immunity perceptibly declined, although many groups continued to address important problems, particularly in the field of organ transplantation. (ABSTRACT TRUNCATED AT 250 WORDS)

Problems in the physiology of class I and class II MHC molecules, and of CD45

1. Co-processing of alloantigens suggests that epitope-loaded MHC class I molecules may pass from tissue cells to dendritic cells. 2. Antigen-presenting cells in the thymus need some special trick in order to load their MHC class II molecules with epitopes from "intermediate concentration" self-proteins in order to induce self-tolerance in developing cells. 3. Cell-cell interactions may transmit signals simply by rearranging surface glycoproteins and thus locally perturbing a phosphorylation equilibrium. 4. The CD45 and STB1 phenotype of most cells in the thymus may be characteristic of a doomed cell.

Immunological activity of a 14-kilodalton recombinant protein of Mycobacterium tuberculosis H37Rv

A 14-kilodalton peptide antigen from Mycobacterium tuberculosis was isolated from an Escherichia coli lambda gt 11 recombinant DNA clone and was identified by Western blotting (immunoblotting) with monoclonal antibody TB68. Immunization of mice and guinea pigs with the recombinant peptide (rTB68) induced in vitro lymphoproliferative responses in draining lymph node lymphocyte cultures as well as in vivo delayed-type hypersensitivity reactions. Moreover, rTB68 was found both to induce and to cross-react with Mycobacterium leprae immune lymphocytes, but did not generate protective effects against live M. leprae challenge in mice. These findings showed that a 14-kilodalton peptide which has been characterized as specific for M. tuberculosis on the basis of B-cell recognition was capable of generating cell-mediated immune responses and moreover contained T-cell epitopes which were cross-reactive with M. leprae antigens.

The structural gene for F liver protein (Flp) maps to chromosome 5 of the mouse

The BXD and AKXL panels of recombinant inbred mouse strains have been typed for the F liver protein alloantigen. The structural gene for F liver protein gene (Flp) is placed on the distal part of chromosome 5, between the known markers Bcd-1 and Gus-s. This excludes the possibility that F liver protein is a major histocompatibility complex molecule, and in turn raises a question about the uniqueness of F and certain other proteins as purgers of self-reactivity among T but not B cells. The typed RI strains have then been used for the immunogenetic studies presented in the succeeding article.

Progress in T cell biology

We outline recent work in our laboratories on thymus progenitors, lineages within the thymus, interactions between regulatory and effector lymphocytes, splitting the CD4 (T4) T cell subset, and Ir and Is genes. We highlight the possibilities for future research opened up by the demonstration that certain marrow-derived cell lines can repopulate thymic lobes in culture, and also the deep insight into the logical structure of the lymph node provided by our ability to make an exact comparison between two-cell-type and three-cell-type immunoregulatory clusters.

Three-cell-type clusters of T cells with antigen-presenting cells best explain the epitope linkage and noncognate requirements of the in vivo cytolytic response

Using an established i.p. adoptive transfer system in which primed precursors of cytolytic (Tc) cells are combined with primed helper (Th) cells and alloantigen, the three-cell-type hypothesis of T-T cooperation has been tested. This hypothesis assumes that cooperation takes place through the formation of clusters, consisting of one or more Tc precursors plus one or more Th cells binding to antigen on the surface of antigen-presenting cells (APC). By using antigens in which the H-2Db epitopes recognized by the Tc precursors are presented either on the same cell as the BALB minor histocompatibility epitopes recognized by the Th cells, or a different one, the value of epitope-linkage has been explored. Epitope-linkage is found to enhance the response at low concentrations of antigen but not at high ones, in accordance with the prediction that at low concentrations individual APC will usually take up either one antigen or the other but not both from an unlinked mixture, while at high concentrations most APC will take up both whether they are linked or not. In a further test of this hypothesis, no requirement for a cognate T-T interaction could be detected. With the three-cell-type interaction thus better established, its implications in terms of efficiency compared with linked-cognate interactions and its evolution are discussed.

Anti-Thy-1 antibody responses evoked by Thy-1 antigen expressed in transfected mouse mastocytoma cells and rat fibroblast

The mouse genomic Thy-1.1 gene was isolated from a phage library constructed from AKR/J (Thy-1.1) mouse DNA. Partial nucleotide sequence analysis of the coding region showed that it has only a single nucleotide difference from the Thy-1.2 gene, namely that amino acid 89 reads CGA (Arg) in Thy-1.1 and CAA (Glu) in Thy-1.2, corresponding to the amino acid substitutions previously identified. It was subcloned into an SV-40 derived vector for transfection. Transient transfection into HeLa cells gave 2% positive staining by immunofluorescence. The gene in this vector was also co-transfected into L cells and mastocytoma cells (both of Thy-1.2 strain origin) together with the Agpt gene. L-cell clones selected for transformation proved almost negative for Thy-1.1 expression, and any positive clones gradually lost Thy-1.1 antigen expression in culture. On the contrary, all clones of mastocytoma transformants gave a high level of expression after more than 3 months in culture. The mastocytoma transformants were used to study the immunogenicity of Thy-1.1 molecules expressed on transfected cells. They evoked clear anti-Thy-1.1 plaque-forming cell (PFC) responses both in vivo and in vitro. The mastocytoma transformants also proved able to induce a T-dependent anti-Thy-1.1 antibody response in a cell transfer experiment. The immunogenicity of Thy-1.2 molecules on rat fibroblasts was also studied after transfection with a Thy-1.2 gene cosmid. Although Thy-1.2 expression was very low, these transfectants elicited a clear anti-Thy-1.2 PFC response from AKR spleen cells hyperimmunized against CBA thymocytes.