T cell clones reactive with sperm whale myoglobin. Isolation of clones with specificity for individual determinants on myoglobin

Analysis of TCR V beta gene usage and encephalitogenicity of myelin basic protein peptide p91-103 reactive T cell clones in SJL mice: lack of evidence for V gene hypothesis

We have analyzed the epitope specificity and encephalitogenicity of peptides that span the C terminus of MBP, p84-103. Our studies show that multiple antigenic epitopes with disease-inducing capacity exist in SJL mice. Three peptides that span this region were examined and found to be immunogenic. However, the mode of immunization (active or passive) determined the incidence and severity of EAE. In our experiments adoptive transfer of p91-103-reactive T cell lines was most consistent in the development of disease. Interestingly, the response to peptides p89-101, p91-103, and p84-102 was absent following immunization with MBP. This suggests that although p91-103 and p89-101 were encephalitogenic they were not the major immunogenic epitopes following immunization with MBP. Analysis of a panel of eight p91-103-reactive T cell clones showed significant heterogeneity in the fine specificity, the TCR V beta gene usage, and in their ability of transfer EAE. These studies suggest that in SJL mice the epitopes involved in the pathogenesis of disease are multiple and there is no clear correlation between encephalitogenicity and TCR V beta gene usage. These observations argue against the presence of a dominant TCR V beta gene in the pathogenesis of EAE in SJL mice.

Unusually diverse T cell response to a repeating tripeptide epitope

The immune system utilizes a diverse T cell repertoire for the recognition of foreign antigens in the context of self MHC gene products. We have examined the potential diversity of the T cell response directed to a immunodominant repeating tripeptide epitope (EYA)5. This peptide represents one of the two T cell epitopes on the synthetic alpha-helical polypeptide antigen Poly 18, Poly EYK(EYA)5 in H-2d mice and does not require antigen processing prior to presentation to Poly 18-specific T cell hybridomas. The T cell response directed to the repeating tripeptide epitope (EYA)5 is extremely heterogenous even though the epitope has a relatively simple amino acid sequence. We have analyzed the fine specificity of 21 randomly chosen Poly 18-reactive, (EYA)5-specific and H-2d-restricted T cell hybridomas derived from H-2d, H-2bxd, and H-2b----H-2bxd Poly 18-responding mice to determine the number of unique antigen reactivity patterns represented by this T cell population. We used alanine- and/or lysine-substituted (EYA)5 peptides and a panel of haplotype-varied splenocytes and observed a great deal of microheterogeneity in response. We find that 13 of the 21 hybridomas have a distinct fine antigen specificity and T cell receptors. The binding of (EYA)5 to the antigen-binding groove of I-Ad appears to generate a highly diversified T cell response. Therefore, (EYA)5-I-Ad complex allows the activation of unrelated T cell clonotypes with the same overall antigen specificity and MHC restriction, but with distinct microheterogeneity in response and receptor usage.

The T cell receptor repertoire influences V beta element usage in response to myoglobin

T cell clones recognizing the sperm whale myoglobin (SpWMb) epitope 110-121 in association with H-2d major histocompatibility complex class II molecules display a very limited heterogeneity of T cell receptor (TCR) V beta usage in DBA/2 mice. All clones previously tested used the same V beta 8.2 gene segment and very restricted junctional regions. To investigate the significance of this observation in vivo, we immunized DBA/2 mice with the intact SpW Mb protein or peptide 110-121. Only the V beta 8+ T cells showed any significant response to the 110-121 epitope. The response to peptide 110-121 was then analyzed in mice which, either as a consequence of antibody depletion or through genetic deletion of TCR V beta genes, lacked V beta 8+ peripheral T cells. DBA/2 mice depleted of V beta 8+ T cells by antibody treatment responded poorly to the 110-121 peptide, and only at high antigen concentrations. In contrast, DBA/2V beta a mice (homozygous for a deletion of multiple V beta gene segments including the V beta 8 family) made a response at least as great as that made by DBA/2 mice, even though the DBA/2V beta a mice had a very restricted TCR V beta repertoire compared with DBA/2 mice. Mechanisms which might determine differences in the 110-121 specific response of DBA/2, DBA/2V beta a and F23.1-treated DBA/2 mice are discussed.

MHC (RT1) restriction of the antibody repertoire to infection with the nematode Nippostrongylus brasiliensis in the rat

It might be expected that infections with transmissible agents will elicit an immune response to all of their exoantigens and that immune response (Ir) gene control of responses to individual epitopes on a given parasite component would be obscured by reaction to the molecule as a whole. Humans infected with parasitic nematodes, however, mount antibody responses which are selective for certain parasite components. This was modelled in inbred rats infected with the parasitic nematode Nippostrongylus brasiliensis and their responses to secreted antigens analysed by immunoprecipitation and SDS-PAGE. No strain responded to all the potential antigens and only those of identical major histocompatibility complex (MHC) had similar recognition profiles. This MHC-restricted response applied to whole molecules synthesized by the parasite, rather than merely to epitopes thereon and is, therefore, contrary to expectation. Moreover, the response patterns of F1 hybrid animals were not merely summations of parental responses. This suggests defective antigen presentation of particular parasite components by certain MHC class II molecules and/or cross-tolerance with background gene products.

The presumptive CDR3 regions of both T cell receptor alpha and beta chains determine T cell specificity for myoglobin peptides

The T cell receptor alpha/beta (TCR-alpha/beta) is encoded by variable (V), diversity (D), joining (J), and constant (C) segments assembled by recombination during thymocyte maturation to produce a heterodimer that imparts antigenic specificity to the T cell. Unlike immunoglobulins (Igs), which bind free antigen, the ligands of TCR-alpha/beta are cell surface complexes of intracellularly degraded antigens (i.e., peptides) bound to and presented by polymorphic products of the major histocompatibility complex (MHC). Therefore, antigen recognition by T cells is defined as MHC restricted. A model has been formulated based upon the similarity between TCR-alpha/beta V region and Ig Fab amino acid sequences, and the crystal structure of the MHC class I and Ig molecules. This model predicts that the complementarity determining regions (CDR) 1 and 2, composed of TCR V alpha and V beta segments, primarily contact residues of the MHC alpha helices, whereas V/J alpha and V/D/J beta junctional regions (the CDR3 equivalent) contact the peptide in the MHC binding groove. Because polymorphism in MHC proteins is limited relative to the enormous diversity of antigenic peptides, the TCR may have evolved to position the highly diverse junctional residues (CDR3), where they have maximal contact with antigen bound in the MHC peptide groove. Here, we demonstrate a definitive association between CDR3 sequences in both TCR alpha and beta chains, and differences in recognition of antigen fine specificity using a panel of I-Ed-restricted, myoglobin-reactive T cell clones. Acquisition of these data relied in part upon a modification of the polymerase chain reaction that uses a degenerate, consensus primer to amplify TCR alpha chains without foreknowledge of the V alpha segments they utilize.

Murine MHC polymorphism and T cell specificities

The major histocompatibility complex (MHC) genes are polymorphic in mouse and man. The products of these genes are receptors for peptides, which while bound, are displayed to T lymphocytes. When bound peptides from antigens are recognized by T lymphocytes, an immune response is initiated against the antigens. This study assessed the relation of the polymorphic MHC molecules to their peptide specificity. The results indicate that although an individual of the species has a limited ability to recognize antigens, the species as a whole has broad reactivity. This rationalizes the extreme polymorphism observed.

Identification and characterization of a mouse cell surface antigen with alternative molecular forms

We present the characterization of a new mouse cell surface protein, recognized by the 3E8-specific monoclonal antibody. The expression of this antigen is predominantly restricted to the hematopoietic and lymphoid tissues: bone marrow, spleen, lymph node, and thymus. Immunoblot analyses show that the 3E8 determinant is present on molecules with different apparent relative masses. The 3E8 antigen migrates on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a single band of Mr 115,000 for normal nonstimulated spleen cells and thymocytes and as two bands of Mr 115,000 and Mr 125,000 for bone marrow cells and mitogen-stimulated spleen cells. The multiple sizes of the 3E8 antigens (isoforms) found on various cell lines are not due to allelic polymorphism, but instead may reflect the specific cell type or reflect the cell's state of activation or maturation. Results from lectin chromatography and N-glycanase and neuraminidase studies suggest that the 3E8 antigen is a heavily sialylated O-linked glycoprotein. The unusual features of this antigen indicate that it may be the mouse homologue of the rat W3/13 antigen and the human leukosialin/sialophorin antigens.

NBxFO factor--a novel suppressor factor produced by fusion of neonatal spleen and a nonsecreting myeloma

Spleens from 1-day-old DBA/2J mice were fused to the nonsecreting myeloma, FO. Dialyzed supernates of these cells were found to suppress the antigen-specific proliferative response of cloned helper or alloreactive T cells at a final concentration of less than or equal to 5%. The same supernate-containing factor did not suppress the response to IL-2 of an IL-2-addicted T cell line. The factor was found not to suppress the production of either IL-2 or antibody, following stimulation of spleen cells with LPS. Absorption analysis revealed that the target of the factor was the accessory cell population. Further experiments indicated that the factor blocked the proliferation of thymocytes due to IL-1. Biochemical analysis revealed a molecular weight for the factor of about 90,000 and a pI of approximately 4.5.

T cell response to myoglobin: a comparison of T cell clones in high-responder and low-responder mice

Mice carrying the H-2b haplotype (e.g., inbred strains C57BL/6 and C57BL/10) are low responders to sperm whale myoglobin when tested in the T cell proliferation assay. Their response is improved by the removal of the Ly-2+ cells from the lymph node population, but it still remains significantly lower than that of cells cells from high-responder strains (e.g., DBA/2, H-2d). To determine whether T cells from the low and high-responder mice recognize the same or different epitopes on the immunizing antigen, we obtained sets of T cell clones from both strains and tested them against peptides representing different regions of the myoglobin molecule, as well as against myoglobins from species other than the sperm whale. Four types of T cell clones were obtained from the DBA/2 mice: 3 types responded to the peptide 107-120 (9 clones altogether), and 1 type responded to the peptide 133-149 (4 clones altogether). The 3 types responding to the peptide 107-120 could be distinguished by their response to horse myoglobin or by the restriction of the response (Ad vs. Ed). Similarly, 5 types of T cell clones were obtained from the C57BL/6 mice: 2 types responded to the peptide 10-22 (1 type, but not the other, responded to horse myoglobin); 1 type responded to the peptide 133-149; and 2 types did not respond to any of the peptides used (1 type, but not the other, responded to dog myoglobin). All 5 types (13 clones altogether) were presumably Ab restricted. These results demonstrate the diversity of epitopes in single antigenic regions and show equivalent heterogeneity of T cell repertoires in high and low responder mice. Attempts to demonstrate specific T cell suppression in the low responder mice failed; only partial, nonspecific suppression was observed.

Two minor determinants of myelin basic protein induce experimental allergic encephalomyelitis in SJL/J mice

Experimental allergic encephalomyelitis (EAE) is an autoimmune demyelinating disease of the central nervous system (CNS) that occurs after immunization of animals with myelin basic protein (MBP). The disease is a prototype model for the study of antigen-specific T helper cell-mediated autoimmune disease. In SJL/J mice, EAE is mediated by T helper cells directed against a 40-amino acid COOH-terminal peptic fragment of mouse small MBP. To identify the minimal T cell epitopes of MBP responsible for EAE, overlapping peptides completely encompassing the epitopes within this region were synthesized. A 28-residue peptide of mouse MBP spanning residues 87-114 (pM87-114) was able to elicit both a strong T cell response and chronic relapsing disease. To better localize the T cell epitopes, shorter peptides within this region were synthesized and two overlapping peptides, pM87-98 and pM91-104, were able to induce EAE. T cell clones and bulk lymph node cell populations reactive with pM87-98 did not respond to pM91-104. However, lymph node cells reactive with pM91-104 also reacted with pM87-98, thus showing that these two peptides represent contiguous, but distinct encephalitogenic epitopes and that both these epitopes may be contained within pM87-98. In addition, pM87-114 and pM87-98 were found to be minor determinants of the total T cell response to rat and rabbit MBP. The restricted response to MBP in SJL/J mice is similar to that of the PL/J mice in that each appears to have only a single peptide region in MBP that elicits encephalitogenic T cells. However, within the region studied, there were two if not more T cell epitopes. This differs from the single encephalitogenic PL/J epitope. These findings of a single encephalitogenic peptide region with multiple T cell epitopes and the fact that encephalitogenic T cell epitopes may be subdominant have implications for the design of treatments directed at the T cell receptor-MHC-peptide epitope complex in autoimmune disease.

Conformation-dependent recognition of a protein by T-lymphocytes: apomyoglobin-specific T-cell clone recognizes conformational changes between apomyoglobin and myoglobin

A T-cell clone specific to apomyoglobin was generated. It was prepared from a T-cell culture obtained by in vitro driving of lymph node cells with apomyoglobin from SJL mice that have been primed in vivo with apomyoglobin. In proliferative assays, the T-cell clone responded to apomyoglobin but did not recognize native myoglobin or any of the synthetic peptides corresponding to the six T sites of myoglobin. The demonstration that a T-cell clone can be isolated, whose specificity is directed entirely to apomyoglobin and not to its counterpart myoglobin, with an identical amino acid composition, indicates the importance of the three-dimensional structure in the presentation of the protein to T cells.

Characterization of subtype-specific and cross-reactive helper-T-cell clones recognizing influenza virus hemagglutinin

The specificity and function of two T-cell clones derived from A/Memphis/1/71 (H3) influenza virus (Mem 71)-immune BALB/c spleen cells have been compared. One clone, X-31 clone 1, was subtype specific, proliferating in response to influenza strains of the H3 subtype only. The other, Jap clone 3, cross-reacted in proliferation assays with heterologous subtypes of influenza A, but not type B. Both clones recognized the HA1 chain of the hemagglutinin (HA) molecule and their proliferation in response to detergent-disrupted virus could be specifically inhibited by monoclonal antibodies to the HA. The T-cell clones were of the L3T4+ phenotype. Both recognized antigen in association with I-Ed, as indicated by studies with H-2 recombinant strains of mice and by blocking with monoclonal anti-I-E antibody. In vivo, both clones elicited a delayed-type hypersensitivity (DTH) reaction when inoculated into mouse footpads together with virus, X-31 clone 1 again displaying subtype specificity and Jap clone 3 being cross-reactive. The clones were also able to provide factor-mediated help in vitro to virus-primed B cells in an anti-HA antibody response. The cross-reactive T-cell clone provided help not only for B cells primed with influenza A subtype H3 and responding to H3 virus in culture, but also for H2 virus-primed B cells making anti-H2 antibody.

Non-specific peptide size effects in the recognition by site-specific T-cell clones. Demonstration with a T site of myoglobin

Six regions (T sites) of myoglobin (Mb) were found by a comprehensive synthetic strategy to stimulate Mb-primed lymph-node cells. To define precisely the N-terminal boundary of the immunodominant T site (residues 107-120) with site-specific T-cell clones and to determine the effects of peptide size on their stimulation, two sets of peptides were employed. In one set, the peptides were elongated to the left from His-113 by one-residue increments of the Mb sequence. The other set represented an identical stepwise elongation by one-residue increments of the Mb sequence, but which were extended by additional unrelated ('nonsense') residues to a uniform size of 14 residues. Examination of the proliferative responses of eight T-cell clones, derived from Mb-primed DBA/2 (H-2d) or SJL (H-2s) mice, revealed a dramatic non-specific size requirement. In every clone, the longer nonsense-extended peptides achieved maximum stimulating activity at a lower optimum peptide dose than its natural-sequence, but shorter, analogue. In addition, slight (one-residue) differences in the N-terminal boundaries among the clones was observed. Thus, the fine specificity of each clone was mapped to the region from residue 111 or 112 to about residue 120 of Mb, which coincides with the site of B-cell recognition and resides in a small discrete surface region of the protein chain.

Role of receptor-binding activity of the viral hemagglutinin molecule in the presentation of influenza virus antigens to helper T cells

The concentration of antigen required to stimulate influenza virus-specific helper T cells was observed to be dependent upon the antigenic form bearing the relevant determinant: intact, nonreplicative virus was needed only in picomolar amounts, while denatured proteins, protein fragments, or synthetic peptides were required in micromolar concentrations for a threshold level of stimulation. Antigenic efficiency of intact virus was found to result from the attachment of virus to sialic acid residues on the surface of the antigen-presenting cell since spikeless viral particles lacking the hemagglutinin molecule were much less efficient antigens for helper T cells and continuous presence of hemagglutination-inhibiting antihemagglutinin antibodies reduced efficiency of stimulation by intact virus approximately 100-fold for both hemagglutinin and internal virion proteins. Influenza virus associated rapidly with antigen-presenting cells; less than 10 min at 20 degrees C was sufficient to introduce virus for a maximal level of T-cell stimulation. This rapid attachment was blocked by antibodies to the hemagglutinin or by pretreatment of the antigen-presenting cells with neuraminidase to remove the cellular virus receptor. Following viral adsorption by antigen-presenting cells, a lag period of 30 min at 37 degrees C was required for the expression of helper T-cell determinants. One early event identified was the movement of the virus to a neuraminidase-insensitive compartment, which can occur at 10 degrees C, but which was not equivalent to expression of helper T-cell determinants. Preincubation of cells with virus at 10 degrees C for 4 h reduced the lag period of helper T-cell determinant expression to 15 min when these cells were shifted to 37 degrees C, suggesting that transition of the virus to a neuraminidase-resistant state is a required step in presentation of T-cell antigenic determinants.

The T cell repertoire for recognition of a phylogenetically distant protein antigen. Peptide specificity and MHC restriction of staphylococcal nuclease-specific T cell clones

Previous studies (1) have indicated that the repertoire of murine T cells specific for a potentially complex protein antigen is in fact specific for a limited number of antigenic epitopes on that antigen in association with a given Ia molecule. Since those studies generally analyzed responses to antigens that differ in only a few amino acids from homologous murine molecules, it was possible that tolerance to self proteins was responsible for the limited T cell repertoire seen in responses to closely related proteins. It was therefore of interest to determine whether T cell recognition of a structurally and phylogenetically more distant protein molecule would also show specificity for a limited number of immunodominant peptides on that molecule. A series of experiments was designed to study the antigen fine specificity and MHC restriction of T cell clones specific for the bacterially derived antigen staphylococcal nuclease (Nase). T cell clones generated in (H-2b X H-2a)F1 (B6AF1) T cells were shown to be specific for Nase and to be restricted by either Ab alpha Ab beta or Ek alpha Ek beta. The fine specificity of these clones was then analyzed using cyanogen bromide and tryptic fragments and a series of overlapping 20-amino-acid synthetic peptides corresponding to and spanning the entire sequence of the Nase molecule. Two Ab alpha Ab beta-restricted clones were highly responsive to peptide 91-110, and not to other synthetic Nase peptides. In contrast, seven Ek alpha Ek beta-restricted clones were consistently responsive to peptide 81-100 and not to 91-110 or to other Nase peptides. Certain of these Ek alpha Ek beta-restricted T cells expressed an interesting crossreactivity, in that they responded to peptide 51-70 as well as to 81-100, although the response to 51-70 was characterized by a markedly shifted dose-response curve, indicating a reduced efficiency of activation by this peptide. Analysis of the amino acid sequences of these regions indicates that this unexpected crossreaction may have a structural basis. A single Nase-specific T cell line generated from BALB/c T cells was, in contrast to any of the B6AF1 clones studied, responsive only to peptide 61-80 and not to other peptides, including 81-100 or 91-110. Collectively, these findings show that Nase-specific T cells are responsive to discrete Nase peptides. Moreover, the present findings suggest that in T cell recognition of a complex and highly foreign protein antigen, a limited number of peptide epitopes are preferentially recognized by T cells in association with a given Ia molecule.

Suicide selection of murine T helper clones specific for variable regions of the influenza hemagglutinin molecule

A negative selection procedure has been developed to obtain murine T helper clones specific for variable regions of the influenza A hemagglutinin. T cell lines, established from mice primed by intranasal infection with X31 (H3N2) virus, were cross-stimulated with natural variant viruses of known primary sequence (either A/TEXAS/1/77 or A/ENG878/69) and proliferating cells eliminated by treatment with the cell cycle-specific drug 5-bromodeoxyuridine. After two suicide cycles, T cell lines were subtype specific and failed to recognize the natural variants. Clones were established by limiting dilution and their specificity was determined against a panel of viruses. Extensive diversity was evident in the reactivity of clones from individual donors, and two major T cell recognition sites were defined in the globular head region of the hemagglutinin molecule.

Peptides related to the antigenic determinant block T cell recognition of the native protein as processed by antigen-presenting cells

A mouse T cell hybrid specific for pigeon cytochrome c in the context of I-Ek responds by secreting interleukin 2 when co-cultured with the native antigen and the B cell lymphoma, LK-35.2, or naive splenic B cells as antigen-presenting cells (APC). Cytochromes c and their corresponding C-terminal fragments which are not capable of stimulating the TPc9.1 cells, including the autologous mouse cytochrome c, block the T cells' response to pigeon cytochrome c. In contrast, nonstimulatory N-terminal peptides of cytochrome c, which share no homology with the antigenic peptide, do not block. Blocking is observed when the nonstimulatory cytochromes c or peptides are present in culture with the live APC and nonsaturating concentrations of pigeon cytochrome c. With tobacco hornworm moth cytochrome c as antigen, a protein for which the T cell has a higher functional affinity, the response of TPc9.1 cannot be blocked by the nonstimulatory cytochromes c or by peptides, even when limiting concentrations of the tobacco hornworm moth cytochrome c are used. When paraformaldehyde-fixed APC are employed, no native cytochrome c can stimulate the T cells, including the tobacco hornworm moth protein which with the live APC is effective at 50 to 100-fold lower concentrations than pigeon cytochrome c. However, with fixed APC the T cells are stimulated by the C-terminal fragments containing residues 81-104 of the pigeon protein or residues 81-103 of the tobacco hornworm moth protein as readily and with the same relative efficiencies as the native protein, presented by live APC. The nonstimulatory peptides, but not the native cytochromes c, block T cell activation by pigeon cytochrome c pulsed-fixed APC, indicating that the nonstimulatory peptides compete with the stimulatory pigeon cytochrome c peptides produced by the APC. This competition appears to be due to nonstimulatory peptides which associate at the APC surface and not to those acting from solution because the APC which have been incubated with pigeon cytochrome c and nonstimulatory peptides and washed free of excess antigen and peptides are not stimulatory to the T cell hybrid. It was concluded that the activation of a pigeon cytochrome c-specific T cell, which recognizes a peptide fragment of the native protein on the surface of an APC, can be blocked by an excess of nonstimulatory homologous peptides when these are also associated on the surface of the APC.(ABSTRACT TRUNCATED AT 400 WORDS)

Extensive diversity in the recognition of influenza virus hemagglutinin by murine T helper clones

A panel of H-2k class II-restricted Th clones were established from individual CBA mice primed by infection with X31 influenza virus. 27 clones, which showed specific recognition of the HA surface glycoprotein, were all H3N2 subtype specific, in contrast to a T cell line which was crossreactive and which may have other specificities. 20 distinct HA-specific clones recognized a tryptic cleavage fragment of X31 consisting of residue 28-328 of HA1 (tops) which includes all the Ab-combining regions of the HA molecule. Seven other HA-specific clones failed to respond to either tops or to aggregate (the remainder of the virus after tryptic cleavage of tops). The specificity of these clones has been mapped, tentatively, to a conformational determinant in the interface antibody-binding region of the HA trimer. Analysis of the fine specificity of the HA-specific clones against a panel of H3N2 natural variant viruses isolated from major virus epidemics from 1968 to 1984 revealed a hitherto unrecognized diversity in T cell recognition of a HA. A total of 12 specificity groupings were evident, and varied from groups of clones that recognized all natural variants to one clone that responded only to isolates from 1968 to 1972. Six out of eight clones from a major specificity group, which failed to recognize variants TX/77, BK/79, or CN/84, responded to two overlapping peptides (48-68 and 53-87), corresponding to a region of HA1 that includes part of two antibody combining sites. An examination of the amino acid sequences of natural variant viruses from this region of HA revealed that residues Asn53 and Asn54 and/or Ile62 were critical for recognition by these clones. We conclude that recognition of HA by Th cells is not restricted to a limited number of epitopes in the conserved regions of the molecule, but is extremely diverse and includes specificities that map to variable antibody-combining regions of the molecule. In addition, the sensitivity of the T cell clones to the amino acid substitutions occurring in HA1 of natural variant viruses suggests that Th may play a role in the immune pressure for antigenic variation in the HA molecule.

One I region restriction determinant can associate with multiple antigenic epitopes

Studies presented in this paper show that T cell clones recognizing different epitopes of multideterminant antigens can be restricted by the same I-A molecule. These data further support the concept that a single I-A restriction site can present more than one antigenic epitope. This concept was supported by data on the proliferation of T cell clones reactive with either poly(L-Glu60, L-Ala30, L-Tyr10)n(GAT) or poly(Tyr, Glu)-poly D,L-Ala--poly Lys [(T,G)-A--L] which recognized different epitopes on these multideterminant antigens. Two clones recognizing different epitopes on the same multideterminant antigen can be blocked by the same monoclonal anti-I-A antibody. Additionally, the mutation in the Abm12 chain utilized in [B6.C-H-2bm12(bm12) X B10.A(4R)]F1 mice can affect the restriction determinant of clones recognizing different antigenic epitopes. These results suggest that in the strictest sense, the determinant selection theory is not tenable and would support the concept that T cell specificity is controlled by the T cell repertoire.

Intrathymic presentation of circulating non-MHC antigens by medullary dendritic cells. An antigen-dependent microenvironment for T cell differentiation

We present evidence for intrathymic presentation of soluble circulating antigens in vivo. Our results show that proteins of different molecular weight enter the mouse thymus rapidly after i.v. injection. The intrathymic presence of antigen was assayed by proliferation of cloned antigen-specific T helper cells, which were cocultured with purified thymic stromal cells; stromal cells were isolated and purified as lymphostromal cell complexes, which preexist in vivo. Antigen presentation copurified with non-adherent medullary dendritic cells (DC) (interdigitating cells). I-A- cortical macrophages forming thymocyte rosettes in vivo and I-A+ cortical epithelial cells forming thymic nurse cells (TNC) in vivo did not act as antigen presenting cells (APC) after antigen pulsing in vivo or in vitro. Thymic APC turn over physiologically and are rapidly replaced (within 2-5 wk) after lethal irradiation by donor bone marrow-derived cells. The frequency of thymocyte-DC interactions in vivo strictly correlates with thymic T cell differentiation, and is independent of the immune status of the animal. Fetal thymic APC seem to be secluded from antigen in the maternal circulation. Thymic DC-ROS probably represent the microenvironment where maturing T cells first encounter non-MHC antigens in the context of self-MHC antigens.

Insulin-specific T cell hybridomas derived from (H-2b x H-2k)F1 mice preferably employ F1-unique restriction elements for antigen recognition

T cell hybridomas of (B10 X B10.BR)F1 genotype with reactivity to bovine insulin (BI) were established to analyze the restriction and antigen fine specificity of (H-2b X H-2k)F1 T cells towards BI. Our data indicate a focusing of the response on two epitopes on the insulin molecule, the A chain loop determinant comprising amino acids A8 and A10, as well as the glutamic acid residue in position 4 of the A chain. Both were recognized either separately or in conjunction. Unexpectedly, the T cell hybridomas exhibited a marked preference for recognizing insulin in the context of F1-unique restriction elements of Ab alpha Ak beta type rather than parental high-responder I-Ab molecules. Analysis of the response of primed lymph node T cells of (B10 X B10.BR)F1 mice towards BI corroborated the finding of a preponderant corecognition of F1-unique I-A molecules.

Characterization of Chlamydia trachomatis serotypes by human T-lymphocyte clones

T cells primed to Chlamydia trachomatis serotypes A, F, and K were cloned by limiting dilution. All T-lymphocyte clones obtained reacted only with C. trachomatis antigens. The proliferative capacity of 89 clones was studied with autologous non-T cells as antigen-presenting cells and the chlamydia serotypes A, B, D, F, K, and LGV-2 as antigens. Most of the clones reacted to several of the chlamydia strains, indicating common antigenic determinants. Other T-cell clones reacted with only a few serotypes. On the basis of the proliferation of the T-cell clones to the chlamydia strains and to interleukin-2, different reactivity patterns were obtained, which possibly can be used to differentiate among the chlamydia strains.

Intrathymic presentation of circulating non-major histocompatibility complex antigens

Intrathymic selection of T-cell specificity has been shown to be influenced by self-major histocompatibility complex (MHC) antigens encoded by radioresistant thymic stromal cells. The role of non-MHC antigens in intrathymic T-cell differentiation, in particular induction of antigen-specific tolerance, has been unclear and the access of non-MHC antigens to the thymus is controversial. Here we present evidence that circulating protein antigens enter the thymus and are presented by thymic stromal cells. At least three distinct types of stromal cells are thought to be associated with intrathymic lymphopoiesis; after intravenous (i.v.) injection of antigen only I-A/E-positive medullary dendritic cells, but not I-A/E-negative macrophages or I-A/E-positive cortical epithelial cells co-purified with antigen-specific stimulation of cloned T-helper cells in vitro. Antigen presentation by thymic stromal cells was dependent on the dose of antigen injected and the time interval after injection.

Multiple functional sites on a single Ia molecule defined using T cell clones and antibodies with chain-determined specificity

Monoclonal antibodies (mAb) were used to inhibit the proliferation of antigen-reactive (C57BL6/J X A/J)F1 restricted T cell clones. We have been able to subdivide these F1 restricted T cell clones into two groups: one of which recognizes the A alpha k A beta b molecule and the other group which recognizes the A alpha b A beta k molecule. Using clones with defined reactivities, we could assign the reactivities of monoclonals to the A alpha or A beta chains. By immunoprecipitation and two-dimensional analysis of Ia molecules from F1 spleen cells, we could independently map the reactivities of the mAb as being determined by the A alpha or A beta chain. To date, these two methods of chain localization of the antibody reactivity have agreed. Further, the differential blocking of the A alpha k A beta b restricted T cell clones suggests that there exists more than one restriction site per Ia molecule. Increasing the number of possible functional Ia restriction sites, either through combinatorial association of alpha and beta chains or by using more than one site per molecule, should increase the number of ways Ia molecules can function in antigen presentation.

Preparation of T-lymphocyte lines and clones with specificities to preselected protein sites by in vitro passage with free synthetic peptides: demonstration with myoglobin sites

Recently, this laboratory has demonstrated that antibodies to preselected regions of a protein can be obtained by immunization with free small synthetic peptides (6-7 residues) without conjugation to a carrier. In the present work, we report the use of free synthetic peptides representing myoglobin (Mb) antigenic sites to prepare T-cell lines and clones of preselected specificities. Lymph node cells from mice primed in vivo with sperm-whale Mb were periodically passaged in vitro with synthetic peptide. After several passages, the peptide-driven long term T-cell cultures responded to the intact protein and exclusively to the peptide that was used to drive the cells. From these cultures, T-cell clones were prepared that responded only to the driving peptide and to the whole protein. The ability to prepare T-cell lines and T-cell clones with preselected submolecular specificities to a protein by driving cultures with desired synthetic peptides affords an important and simple tool for basic immunological investigations and for clinical applications.

Influenza virus site recognized by a murine helper T cell specific for H1 strains. Localization to a nine amino acid sequence in the hemagglutinin molecule

The functional helper T cell line Vir-2, derived from a PR8 (H1N1) influenza virus-immunized BALB/c mouse, proliferates in response to syngeneic antigen-presenting cells and naturally occurring strains of subtype H1 human influenza virus from 1934-1957 and 1977-1980 isolates. A conserved region of the hemagglutinin molecule around amino acid position 115 in the heavy chain (HA1) was implicated as being important in this recognition by the lack of stimulatory activity associated with a glutamic acid to lysine substitution at position 115 in the laboratory mutant RV6, derived from wild-type PR8. Characterization of the stimulatory determinant on the wild-type hemagglutinin molecule was then undertaken using cleavage products and synthetic peptides. Vir-2 cells recognized the reduced and alkylated purified HA1 of PR8 virus, and this reactivity was retained after cleavage at methionine and tryptophan residues. High-pressure liquid chromatography separation of cleavage fragments indicated that a short sequence of the HA1 containing residue 115 was being recognized. This recognition was localized to a nine amino acid segment (positions 111-119) by assaying stimulation with synthetic peptide homologues of different lengths from that region. As with native hemagglutinin, Vir-2 cells responded to active peptides when presented by H-2d but not H-2k antigen-presenting cells.

T cell clones specific for hybrid I-A molecules. Discrimination with monoclonal anti-I-Ak antibodies

Alloreactive and soluble antigen-reactive, I-A-restricted T cell clones were examined for their ability to recognize hybrid I-A antigens. Several clones that recognized hybrid I-A(b)/I-A(k) molecules on (C57BL/6 x A/J)F(1) [(B6A)F(1)] spleen cells were studied. We were able to distinguish clones that recognized hybrid I-A molecules of the A(b)(a)A(k)(beta) type from those that recognized A(k)(a)A(b)(beta) molecules. We reached this conclusion by considering data from three independent types of experiments. (a) Monoclonal antibodies were used to inhibit T cell stimulation. Antibodies 10.2.16 and H116.32 distinguished two mutually exclusive "families" of T cell clones. One group of clones was inhibited by 10-2.16 and not H116.32, the other group exhibited reciprocal inhibition. (b) T cell proliferation was assayed using antigen-presenting cells from B6.C-H-2(bml2) (bml2) and [bml2 x B10.A(4R)]F(1) mice. Because the bml2 strain has a mutation that results in an altered A(b)(beta) polypeptide chain (A(bm12)(beta)), we reasoned that clones that could recognize the [bm12 x B 10.A(4R)]F(1) cells were recognizing A(b)(a)A(k)(beta) molecules. Alternatively, clones not recognizing [bml2 x B10.A(4R)]F(1) cells had specificity for A(k)(a)A(b)(beta) molecules. (c) I-A molecules immunoprecipitated from radiolabeled (B6A)F(1) splenocyte extracts were analyzed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These experiments confirmed an earlier report that antibody 10.2.16 recognized determinants on the A(k)(beta) chain (12). Antibody H116.32 immunoprecipitated products consistent with recognition of A(k)(a) determinants. Taken together, these three types of results offer conclusive evidence that T cell clones recognizing "hybrid" I-A molecules use either A(b(k)A(k)(beta) or A(k)(a)A(b)(beta) molecules as recognition or restriction sites. Clones whose proliferation was supported by [bm 12 x B10.A(4R)]F(1) cells and blocked by anti-I-A(k) antibody 10-2.16 recognized A(b)(a)A(k)(beta) B molecules. Clones that were blocked by antibody H116.32 and did not recognize [bml2 X B10.A(4R)]F(1) cells use a recognition site(s) on A(b)(a)A(k)(beta) molecules. Thus, we can demonstrate both functionally and biochemically that hybrid F(1) I-A molecules of the structure A(k)(a)A(b)(beta) and A(b)(a)A(k)(beta) both exist on (B6A)F(1) splenocytes and that both configurations are used in immune recognition phenomena.

T-cell proliferative response to hapten-modified self-immunoglobulins: recognition of conjugate-specific determinants

(4-Hydroxy-3-nitrophenyl)acetyl (NP)-modified BALB/c immunoglobulins were used as the immunogen for induction of a proliferative response in BALB/c mice. As is true for responses to other soluble antigens, proliferation was dependent on Lyt-1 cells and histocompatible radioresistant accessory cells. Lyt-1 cells directed against NP-modified self immunoglobulin are specific for the immunizing hapten NP. However, they do not recognize hapten per se. Rather, they see complex determinants comprised of both the hapten NP and the immunoglobulin self-carrier. Distinct specificities were created by coupling the same hapten to different monoclonal BALB/c antibody molecules or by attaching the hapten to the immunoglobulin self-carrier via a spacer molecule. It is proposed that determinants created by attaching haptens to self-immunoglobulin molecules are similar to those recognized by anti-idiotypic T cells.