Characterization of T-cell surface proteins bound by heterologous antisera to antigen-specific T-cell products

Messenger RNA for an antigen-specific binding molecule from an antigen-specific T-cell hybrid

The T-cell hybridoma 51H7D specifically binds the hapten azobenzenearsonate (ABA). An antiserum (anti-PCIF) specific for antigenic determinants shared by antigen-binding molecules of T cells (TABM) was used to precipitate polyribosomes containing mRNA for TABM from this T-cell hybridoma. The resultant mRNA was translated in vitro. The translated product (TrP51H7D) bound specifically ABA and was bound by both anti-PCIF and anti-T-cell suppressor factor. The parent lymphoma BW5147 yielded a similar translated product with the same antiserum used to isolate specific mRNA containing polysomes. This product (TrPBW) was bound by the antiserum used but did not bind ABA. The specific translated protein from both cells had a pI of approximately equal to 5.0, and apparent molecular weight of 71,000 (reduced) or 145,000 (nonreduced). Both protein products, when treated with guanidine to break down all noncovalent bonds, revealed an elemental peptide of Mr 23,500. The cDNA made from the isolated mRNA had 600-900 bases. mRNA of this size is expected for a protein of Mr 25,000. Our data indicate that a TABM specific for ABA is composed of peptides of Mr 23,500.

T cells produce an antigen-binding factor with in vivo activity analogous to IgE antibody

T cell-dependent activation of resident tissue mast cells is required for the elicitation of delayed-type hypersensitivity skin reactions in mice. A T cell-derived antigen-binding factor that transfers the ability to elicit an immediate hypersensitivity-like skin reaction is described and compared with a hybridoma IgE antibody. Both the T cell factor and IgE mediate reactions with increased vascular permeability and both are mast cell dependent, as they are inactive in two different types of mast cell deficient mice (W/Wv and Sl/Sld). The T cell factor was distinguished from IgE by affinity chromatography using specific anti-IgE and anti-factor antibodies and by a shorter duration of passive sensitization. The T cell factor is a suitable candidate for participation in the mechanism by which T cells activate mast cells in delayed-type hypersensitivity.

Use of anti-idiotype immunosorbents to isolate circulating antigen-specific T cell-derived molecules from hyperimmune sera

We immunized four different sheep with antigen-binding material found in the serum of BALB/c mice 4 days after primary immunization with sheep erythrocytes (SRBC). The resultant antibodies made by the sheep contained a specificity(ies) that appeared to react with a dominant idiotype present on SRBC-specific Lyt-2+ T cells. The antiserum made by the sheep markedly inhibited the formation of antigen-specific rosettes by SRBC educated T cells but did not inhibit T cells educated to other heterologous erythrocytes from forming crossreacting rosettes with SRBC or specific rosettes with the homologous erythrocytes. The "anti-Id serum" was depleted of all activity against known immunoglobulin isotypes and light chains and then was used to isolate antigen-binding molecules from mice that were hyperimmunized with SRBC. The ShId+ material so isolated could be divided into two main groups--one that expressed immunoglobulin determinants, and one that did not. The former represented 15-25% of the ShId+ protein isolated and comprised a minority of the anti-SRBC antibody in the anti-SRBC serum; the latter group of proteins bound sheep glycophorin specifically and expressed constant region determinants found on a number of other antigen-specific T cell factors. These experiments suggest that antigen-binding molecules made by T cells display much less heterogeneity than do antibodies and also show that the serum of hyperimmune mice contains significant amounts of T cell-derived antigen-specific immunoregulatory molecules.

Genetic chasing of T helper cell idiotype and allotype genes

The present experiments were performed to study whether the genes responsible for the expression of T-idiotypes and allotypes could be mapped in relation to immunoglobulin (Ig) heavy chain V- and C-genes. Use was made of our antiserum 5936, which detects idiotypes in B6 and anti-B10.BR sera and on Lyt-1+, 2.3-B6 anti-B10.BR T-cell populations, and antiserum 6036, which detects allotypes on Lyt-1+, 2.3-B6 T cells, but which does not react against Ig. The reactivity of these antisera with T cells from (B6 X C3H.OH) X C3H.OH backcross mice and CBA-allotype congenic B6 mice was investigated because 5936 idiotypes and 6036 allotypes appeared to be associated with Igh-1b genes (B6) and not with Igh-1j genes (C3H.OH,CBA). Our results will show, first, that 5936 idiotypes on Lyt-1+, s.3-B6 anti-B10.BR T cells are synthesized by genes linked to Igh-1b allotype genes and they are situated either within Ig heavy chain V-genes or centromeric to them. Second, our results will show that 6036 allotypes on Lyt-1+, 2.3-B6 T cells are produced by genes also linked to Igh-1b-allotype genes, and the 6036 allotype genes are situated between Ig-VH and prealbumin genes.

Antigenic polypeptide fragments of a receptor related to the Fab fragment of human immunoglobulin from thymus-derived lymphocytes

Certain thymus-derived lymphocytes of man and other primates express surface components related to the variable region of immunoglobulin heavy chains but lack constant region determinants defining any known immunoglobulin class. To obtain structural information on this molecule that can be used for comparison with known immunoglobulins and other surface molecules, we isolated the T cell-derived molecule by affinity chromatography using an antiserum raised against the monomeric Fab fragment of a human Waldenström macroglobulin and subjected the isolated molecule to either proteolysis using enzymes or cleavage with cyanogen bromide, followed by isolation of polypeptides which bore the Fab- or heavy chain variable region (VH)-related antigenic markers. The intact T cell molecule had an apparent mass of 68,000 daltons and no evidence was found for covalent or noncovalent association with polypeptides resembling light chains in apparent mass. The pattern of fragments obtained by cleavage of the T cell heavy chain suggests that the molecule is comprised of domains of approximate mass 12,000 daltons. Isolation of fragments from the digests that bear Fab-related serological markers shows that the molecule can be degraded into fragments resembling the Fd and VH of standard immunoglobulin heavy chains. A procedure was developed enabling the isolation of milligram quantities of VH-related T cell products. These results support the concept of a sharing of combining site determinants between T cell receptors and immunoglobulin heavy chains and show a general formal similarity between the two classes of molecules, even though they lack shared constant region determinants. The susceptibility of the T cell molecule to be cleaved into discrete antigenic fragments by controlled proteolysis might help to explain the plethora of sizes observed for antigen-specific T cell factors.

Transfer of an antigen-specific immediate hypersensitivity-like reaction with an antigen-binding factor produced by T cells

The fact that T cell-dependent activation of mast cells occurs in delayed-type hypersensitivity led us to investigate whether a T cell product could mimic some of the functions of IgE. We report that 24- or 48-hr cultures of T cells from mice immunized optimally for delayed-type hypersensitivity resulted in release of an antigen-binding factor that transferred the ability to elicit an antigen-specific immediate hypersensitivity-like skin reaction in normal recipients. The responsible factor was concentrated and purified by affinity chromatography on antigen columns and was distinguished from immunoglobulin by several criteria: (i) it was released by purified T cells (anti-immunoglobulin plate depletion of B cells); (ii) it expressed no known antigenic markers of immunoglobulins (enzyme-linked immunosorbant direct binding assay); (iii) it had a molecular weight of 70,000 or less (sucrose gradient ultracentrifugation); and (iv) it had serological markers associated with antigen-specific T cell factors from other experimental systems. We suggest that, at sites of delayed-type hypersensitivity, antigen-reactive T cells may release antigen-specific factors that lead to mast cell activation and release of vasoactive amines, which is required for elicitation for these responses.

The isolation of an antigen binding factor from cultured murine T-lymphocytes

BALB/c mice were immunized with the random sequence polypeptide [Glu60 Ala40] (GA). 125I-lymphocyte suspensions were prepared from lymph nodes, radiolabelled with 125I and cultured for 18 hours. Supernatant fluids were collected and passed over an immunoabsorbant composed of [D-Glu60 D-Ala40] (D-GA) bound to Sepharose. The non-adherent fraction was then applied to GA Sepharose and the adherent material eluted with 2 M NaSCN. The eluate was relabelled with 125I, reabsorbed to GA Sepharose and eluted. This fraction bound well to GA-Sepharose (50-80%) but not to the enantiomorphic D-GA Sepharose (5-10%). This material did not react with goat antisera directed against murine IgG, IgM or IgA. It was capable of binding to rabbit antiidiotypic sera raised against BALB/c anti-GA, but not to those antibodies raised against BALB/c anti-GAT. It also showed some reaction with rabbit antiserum to a rat T cell factor (TCF). Polyacrylamide gel electrophoresis revealed a major component with an approximate molecular weight of 63,000 which was not affected by reduction and alkylation.

Detection of T cells that secrete molecules which share determinants with antigen-specific T-cell factors

A single-cell secretion assay was used to detect cells that secrete products which react with an antiserum that binds T cell antigen-binding polypeptides. The antiserum (R11), which was produced by immunization of rabbits with a murine trinitrophenyl-specific suppressor factor, reacts with T cells and their products and with a suppressor T-cell clone but not with B cells or their products. The secretory cells this antiserum detected were found to be unevenly distributed among various organs (spleen, lymph node, and thymus) and, to different degrees, in spleens of various strains of mice. In unimmunized CBA/J mice, approximately 1-3% of spleen cells secreted macromolecules precipitable by R11. The majority of the secretory cells could be removed by panning with a mixture of Ly 1 and Ly 2 antibodies but not with either antibody alone. This is consistent with the cells having low surface antigen densities as a result of being either "pre-T" cells or mature secretory cells analogous to B-lineage plasma cells. In agreement with the latter possibility was our finding that the secretory activity of cells detected with antisuppressor factor was comparable to that of Ig-secretory cells as detected with an anti-Ig antiserum. However, higher numbers of R11+ secretory cells were seen in the immunoglobulin-negative fraction of spleen cells from nude mice, which could be interpreted to favor the first possibility. In either case this study shows that the single-cell assay technique is well suited for the detection and characterization of molecules released by immunoregulatory T cells.