T cell surface I-J glycoprotein. Concerted action of chromosome-4 and -17 genes forms an epitope dependent on alpha-D-mannosyl residues

Binding of the two polypeptide chains of dengue virus-induced suppressor cytokine to its receptor isolated from macrophages

Dengue type 2 virus (DV)-induced suppressor cytokine (SF) is composed of two polypeptide chains (alpha and beta) and has a receptor on macrophages (M phi), which has been purified. The present study was undertaken to study the binding of the two polypeptide chains of SF to M phi and its purified receptor (SF-R) protein. It was observed that both alpha and beta-chains of SF, purified by high performance liquid chromatography (HPLC), bound to M phi cell, but only alpha-chain bound to SF-R protein. Only H-2A positive M phi bound SF. Anti-H-2Ak mAb blocked the binding of SF to M phi but had no effect on binding of SF to SF-R. Both anti-SF-antiserum and anti-SF-R-antiserum blocked the binding of SF to M phi. The binding of the beta-chain of SF to M phi was blocked by anti-H-2Ak mAb while the anti-SF-R-antiserum blocked the binding of alpha-chain on M phi. Thus, the alpha-chain of SF binds to SF-R and the beta-chain binds to H-2A determinants on M phi.

Dengue virus-induced helper cytokine has two polypeptide chains which bear different determinants

Dengue type 2 virus (DV) induces generation of a T cell helper cytokine (HF) in mouse spleen which enhances the antigen-specific antibody plaque forming cell count in syngeneic mice. The present study was undertaken to investigate the molecular structure of HF. It was observed that the activity of HF was abrogated by treatment with reducing agents such as glutathione, ouabain or dithiothreitol (DTT) which cleave disulphide bonds, separating the polypeptide chains. The two polypeptide chains could be purified by high performance liquid chromatography of DTT treated HF. The individual chains had no helper activity, but it could be restored by mixing the two. One chain of the HF bonded to the DV-antigen coupled immunosorbent column and the other to the anti-I-Ak antibody coupled column. Thus, DV-induced HF is a disulphide bonded double chain structure, one chain having antigen and the other having I-A determinants; the presence of both chains is essential for helper activity.

Molecular genetic characterization of the mRNA coding for an inducible suppressor factor specific for L-glutamic acid60-L-alanine30-L-tyrosine10

The suppressor T-cell hybridoma 1556A2.1 can be induced by the monoclonal L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT)-specific suppressor inducer 372B3.5 and soluble GAT to synthesize a disulfide-linked heterodimeric protein (GAT-TsF2), which directly suppresses a primary in vitro immune response to GAT. Induction and synthesis of the GAT-TsF2 protein is correlated with the appearance of specific mRNA, as detected by translation in vitro in a wheat germ cell-free extract of RNA isolated at various times after induction. The mRNA coding for the polypeptide chain that bears a serologically defined I-J determinant (I-J+ chain) appeared 8 hr after induction, whereas the mRNA coding for the antigen-binding chain (AB+ chain) was not detected until 16 hr after induction. The mRNAs coding for the individual chains sedimented as different species, suggesting that the two-chain factor is the product of two genes. The AB+ chain of the 1556A2.1 GAT-TsF2 was synthesized on membrane-bound polysomes, whereas the I-J+ chain was translated on free polysomes. The AB+ chain was synthesized from two independent mRNA species sedimenting at 10 S and 28 S, whereas a single 16S mRNA encoded the I-J+ chain. The in vitro translated I-J+ chain was bound by a monoclonal antibody against the I-J+ determinant of only the appropriate H-2 haplotype. These results suggest that posttranslational modification, including glycosylation, is not required for biological activity or for expression of the I-J epitope on the GAT-TsF2 molecule.

Virus-induced immunosuppression

Infection with a variety of viruses results in the suppression of the host's immune system. Several mechanisms thought to be responsible for this effect are discussed: infection and alteration of lymphocytes and macrophages, production of soluble suppressor factors, and the induction of suppressor cells. The clinical significance of virus-induced immunosuppression is also discussed.

Differences in cellular immune response to L-glutamic acid60, L-alanine30, L-tyrosine10 (GAT) in full sibling embryo transfer cattle: examination of requirements for cell proliferation

Pairs of full sibling embryo transfer cattle that expressed identical MHC class I and II products were tested for their in vitro proliferative response to GAT. Peripheral blood mononuclear cells from these cattle were either high or low responders to GAT. Cells from certain pairs of MHC identical siblings gave opposite responses. Low responder animals were further tested to determine if they might respond to GAT with different kinetics, with secondary in vitro restimulation, or with exogenous help provided by interleukin 2. Also, the role of antigen presenting cells and suppressor T cells from low responder animals was investigated. Using appropriate in vitro conditions, cells from all animals tested could respond to GAT. However, MHC identical animals tested under similar conditions exhibited differences in their response to GAT which suggests the proliferative immune response was influenced by factors in addition to MHC coded products.

Regulation of synthesis of N-linked glycoproteins and their lipid intermediates in human T lymphoblastoid cells

The synthesis of N-linked glycoproteins and their lipid intermediates was investigated in cell-free preparations of human T lymphoblastoid cells during two phases of cell growth. The incorporation of 14C-labeled Man into glycoproteins and dolichol-linked oligosaccharides was greater during the logarithmic growth phase than the stationary phase. The incorporation of 14C-labeled GlcNAc into dolichol derivatives was increased in the logarithmic phase. However, the synthesis of Dol-P-Man was not significantly different. These data suggest that the differences are due, at least partially, to the increased synthesis of Dol-P-P-GlcNAc.

I-J epitopes are adaptively acquired by T cells differentiated in the chimaeric condition

I-J has been defined as a locus mapped in the murine major histocompatibility complex (MHC) which encodes serological markers found primarily on the surface of suppressor T cells (TS) and soluble suppressor factors (TSF). Recent studies have, however, revealed that there is no such specialized locus within the MHC at the DNA level. As the existence of I-J determinants at the protein level on functional T cells, T-cell clones and hybridomas has been confirmed by several serological and biochemical studies, this contradiction has raised serious arguments in the immunological community concerning the nature, origin and expression of I-J determinants. We have raised a number of monoclonal antibodies against the polymorphic structure of I-J molecules, and have studied the expression of I-J epitopes on T cells derived from irradiated bone marrow chimaeras in which stem cells of different genotype differentiated into T cells under the foreign host MHC environment. The results, presented here, indicate that I-J epitopes are not primarily determined by the MHC genes of the stem cells themselves, but are adaptively acquired by T cells differentiated in the chimaeric condition according to the environmental MHC phenotype. Thus, the serologically detectable I-J epitopes are found to be associated with inducible T-cell receptors recognizing self class II MHC antigens.

Two-chain disulphide-bonded structure of antigen-specific T-helper factor: both chains are necessary for activity and their interaction is I-A restricted

The molecular structure of the antigen-specific T-helper factor (ThF) which augments contact sensitivity in mice was studied. ThF was split into two types of polypeptide chain by mild reduction and alkylation; one antigen binding (which determined the specificity), the other non-antigen binding. The two chains were, by themselves, inactive but complemented each other and reconstituted biological activity. In addition, a genetic restriction was observed in the complementation of the two chains which mapped to the I-A subregion of the H-2 complex.

A role for suppressor T cells in induction of self-tolerance

The potential role of suppressor T cells (Ts) in the induction of self-tolerance was investigated by eliminating I-J+ cells during ontogeny (I-J antigens are encoded by the I-J subregion of the murine major histocompatibility complex). To achieve this, F1 mice were exposed to anti-I-J antibodies via the transplacental route by mating B10.A(3R) females, preimmunized with B10.A(5R) cells, with CBA males. At 6 weeks of age, the offspring were injected with rat erythrocytes (RRBC) to induce erythrocyte autoantibodies. By comparison with age-matched controls, Ts-depleted mice produced significantly higher titers of autoantibody, whereas there was no difference in the antibody response of the two groups to the foreign determinants on the RRBC. The selective increase in autoantibody production was mirrored at the clonal level by the appearance of self-reactive B-cell hybridomas after fusion of RRBC-immune spleen cells with the NS-1 cell line. On the other hand, when helper cell function of RRBC-primed cells was measured in a T-cell proliferative assay, Ts depletion in utero resulted in enhanced T-cell activity to nonself (RRBC) but not to self (mouse erythrocyte) determinants. Thus, helper T cells recognizing nonself determinants on RRBC appeared to be responsible for activating self-specific B cells, presumably through linked recognition of different epitopes on mouse erythrocytes. Taken together, these findings indicate that elimination of I-J+ cells during ontogeny can lead to the appearance and activation of "forbidden" B-cell clones and points to a central role for Ts in induction as well as maintenance of self-tolerance.

Tubular antigen-derivatized cells induce a disease-protective, antigen-specific, and idiotype-specific suppressor T cell network restricted by I-J and Igh-V in mice with experimental interstitial nephritis

The nephritogenic effector T cell response producing interstitial nephritis in mice can be largely inhibited by the adoptive transfer of suppressor T cells before or after the induction of disease. These suppressor T cells are harvested from donor mice primed with tubular antigen-derivatized syngeneic lymphocytes, and two subsets of suppressor cells can be characterized within this donor cell population. The first suppressor cell in this network is an L3T4+, I-J+, RE-Id+ cell (Ts-1). Ts-1 cells are antigen-binding suppressor cells that inhibit afferent phase immune responses and, in the presence of tubular antigen, specifically induce Lyt-2+, I-J+ cells (Ts-2) that are antiidiotypic (RE-Id-binding) suppressors. The Ts-2 cell is functionally restricted in its suppressive effect by I-J and Igh-V gene products, and acts on the effector limb of the cell-mediated anti-tubular basement membrane immune response. These studies provide an experimental basis for further efforts to use immunoregulatory modulation in the control of autoimmune renal disease.

The Thy-1-bearing cell of murine epidermis. A distinctive leukocyte perhaps related to natural killer cells

Bone marrow-derived leukocytes of murine epidermis can express two phenotypes: typical Langerhans cells, which are Ia+ and Thy-1-, and a recently discovered second population that is Thy-1+ and Ia-. To verify that these phenotypes are expressed by two different cell types, and to help understand their lineage and function, we have studied morphology and reactivity with a large panel of antibodies. Dual antibody immunofluorescence combined with electron microscopy showed that Thy-1+ and Ia+ cells were each distributed in a regular fashion and formed adjacent dendritic systems in or close to the basal layer. Double-labeling studies with anti-Ia and a second monoclonal antibody revealed that all Langerhans cells expressed F4/80 (macrophage), Mac-1 (C3bi receptor), and 2.4G2 (Fc receptor), as well as the thymus leukemia (TL) and heat-stable (M1.69/16) antigens. A large fraction expressed S100 and all exhibited membrane ATPase and nonspecific esterase. In contrast, Thy-1+ cells lacked all these features of Langerhans cells, except that a minority were strongly reactive with 2.4G2. Thy-1+ cells also lacked differentiation antigens of most other types of leukocytes, except they were rich in asialo GM1. By electron microscopy, Thy-1+ cells had cytoplasmic granules that were similar in structure and in their aryl sulfatase content to those previously described in natural killer cells. The granules were enlarged in beige mice, suggesting a lysosomal origin, and were present in mast cell-deficient W/Wv mice, indicating no relation to mast cells. We conclude that Thy-1+ epidermal cells are thoroughly distinct from Langerhans cells. On the basis of morphology and phenotype, they may represent a type of tissue natural killer cell. Thy-1+ natural killer cells are now being identified in several nonlymphoid sites, such as gut epithelium and the livers of mice given adjuvants. If Thy-1+ epidermal cells prove to be natural killer cells, it is noteworthy that they represent a resident population regularly distributed in the basal layer of all mouse strains. The notion that Thy-1+ epidermal cells are immature natural killer cells is intriguing in light of recent evidence that Ia+ Langerhans cells are also immature with respect to accessory cell function. The epidermis may not have the functional capacities of a lymphoid organ, but it could contribute immature cells important for both natural and acquired resistance.

The I-J glycoprotein: genetic control, biochemistry, and function

The I-J molecule is a mannosylated protein expressed early in T cell ontogeny in partially shielded form, later fully exposed on an activated T cell subset. Others determined a 25-30,000 molecular weight for cellular (Kumagai et al. 1984) and secreted forms (Taniguchi et al. 1984). Both the cell membrane and secreted types seem to govern genetically-restricted interactions completing suppressor cell circuits. The soluble I-J polypeptide has no antigen-binding site, but associates with an antigen-binding chain via disulfide bonding (Taniguchi et al. 1984, Lei et al. 1983). Similarly, evidence suggests that cellular I-J molecules are part of or proximal to T cell antigen receptor complexes (Fig. 4). At least two genes control T cell I-Jk expression, one apparently in I-E, another on chromosome 4. Undiscovered loci may also participate. Since I-J+ T cells do not transcribe I-region DNA, the I-E gene must be an untranscribed regulatory element in T cells or a protein translated in the host environment. If in the host environment, it probably does not function enzymatically to form T cell I-J epitopes; removed from the host, T cells biosynthesize complete I-J determinants. Host I-E gene products may regulate I-J expression in an early T cell maturation step. For example, the E alpha E beta proteins of thymic macrophages and epithelial cells may drive the expansion of T cells with E alpha E beta-complementary receptors encoded by I-J genes outside H-2. Genetic control of this self receptor would then apparently map to the selective ligand gene, I-E, as well as the I-J structural gene elsewhere (Klyczek et al. 1984b). This attractive theory, proposed in its original form by Jerne (1971) and later by Schrader (1979), has received significant support. Definitive proof must await further experimentation.

A new thymocyte membrane differentiation antigen for mouse and rat

A new thymocyte membrane-brain antigenic system is defined for the mouse and rat. Monoclonal antibody NIM-M129 recognizes a membrane antigen that has a similar size to Thy-1 (20-23 kd) but entirely different tissue distribution. It is absent from cortisone-resistant thymocytes, murine peripheral T cells, T-cell blasts, and T-cell lymphomas, or rat bone marrow. However, the determinant exhibits a quantitative difference in expression on thymocytes of Thy-1a (low) and Thy-1b (high) mice, with intermediate values for their F1 progeny. Backcross and F2 segregation tests between CBA and CBA-Thy-1a congenic lines established firm genetic linkage between Thy-1 and the level of epitope expression on the thymocyte cell surface.

Activation of T lymphocytes results in an increase in H-2-encoded neuraminidase

The endogenous neuraminidase activity of various mouse lymphoid subpopulations and tissue compartments was examined by a sensitive fluorometric assay. These analyses indicated that activated T lymphocytes possessed a significantly higher level of intracellular neuraminidase than activated B or resting T or B lymphocytes. Examination of the level of neuraminidase in bone marrow, thymus, lymph node, and unfractionated spleen indicated that these lymphoid tissues contained significantly less neuraminidase than was detected in stimulated T cells. Kinetic studies revealed that the majority of the increase in neuraminidase activity occurred between 24 and 48 h following stimulation. Analysis of activated T lymphocytes prepared from a panel of inbred mouse strains indicated that cells from mice of the H-2v haplotype, which possess the Neu-1a allele and are deficient in liver neuraminidase, exhibited a level of activity which was significantly lower than that detected in stimulated T cells from other mouse strains. These results indicate that the endogenous neuraminidase activity of T lymphocytes increases upon stimulation, and that the level of this enzyme activity in lymphoid cells is also controlled by the Neu-1 locus, which is located in the H-2 region of the major histocompatibility complex.