Intranasal immunization with cytotoxic T-lymphocyte epitope peptide and mucosal adjuvant cholera toxin: selective augmentation of peptide-presenting dendritic cells in nasal mucosa-associated lymphoid tissue

We previously reported that cholera toxin (CT) was required as a mucosal adjuvant for the induction of peptide-specific cytotoxic T lymphocytes (CTL) following intranasal immunization with CTL epitope peptides (A. Porgador et al., J. Immunol. 158:834-841, 1997). The present study was performed to identify the site and the antigen-presenting cell (APC) population responsible for the presentation of intranasally administered CTL epitope peptide immunogens and to determine whether CT directly affects antigen presentation by these APCs. For these experiments, C57BL/6 mice were intranasally immunized with the ovalbumin H-2Kb-restricted CTL epitope SIINFEKL with or without CT. Cells were then isolated from the cervical lymph nodes (CLN) and the nasal mucosa-associated lymphoid tissue (NALT) and tested for the ability to stimulate the B3Z T-cell hybridoma, which recognizes SIINFEKL in association with H-2Kb. Dendritic cell (DC)-enriched CLN cells from mice immunized with peptide and CT or peptide only could stimulate B3Z cells, while DC-depleted CLN cells from either group were unable to stimulate B3Z cells. NALT cells of mice immunized with peptide and CT, but not with peptide alone, were able to efficiently stimulate B3Z hybridomas. Depletion of N418-positive DC from these NALT cells resulted in significant reduction of B3Z activation. Our results indicate that DC are the APC responsible for the presentation of CTL epitope peptides following intranasal immunization and that CT augments the ability of dendritic cells in the NALT, but not in the draining CLN, to present CLT epitope peptides. This finding suggests that CT acts locally as a mucosal adjuvant and that NALT DC are the predominant APC involved with the induction of immunity after intranasal immunization with peptide immunogens and CT.

Immunization with a single major histocompatibility complex class I-restricted cytotoxic T-lymphocyte recognition epitope of herpes simplex virus type 2 confers protective immunity

We have evaluated the potential of conferring protective immunity to herpes simplex virus type 2 (HSV-2) by selectively inducing an HSV-specific CD8(+) cytotoxic T-lymphocyte (CTL) response directed against a single major histocompatibility complex class I-restricted CTL recognition epitope. We generated a recombinant vaccinia virus (rVV-ES-gB498-505) which expresses the H-2Kb-restricted, HSV-1/2-cross-reactive CTL recognition epitope, HSV glycoprotein B residues 498 to 505 (SSIEFARL) (gB498-505), fused to the adenovirus type 5 E3/19K endoplasmic reticulum insertion sequence (ES). Mucosal immunization of C57BL/6 mice with this recombinant vaccinia virus induced both a primary CTL response in the draining lymph nodes and a splenic memory CTL response directed against HSV gB498-505. To determine the ability of the gB498-505-specific memory CTL response to provide protection from HSV infection, immunized mice were challenged with a lethal dose of HSV-2 strain 186 by the intranasal (i.n.) route. Development of the gB498-505-specific CTL response conferred resistance in 60 to 75% of mice challenged with a lethal dose of HSV-2 and significantly reduced the levels of infectious virus in the brains and trigeminal ganglia of challenged mice. Finally, i.n. immunization of C57BL/6 mice with either a recombinant influenza virus or a recombinant vaccinia virus expressing HSV gB498-505 without the ES was also demonstrated to induce an HSV-specific CTL response and provide protection from HSV infection. This finding confirms that the induction of an HSV-specific CTL response directed against a single epitope is sufficient for conferring protective immunity to HSV. Our findings support the role of CD8(+) T cells in the control of HSV infection of the central nervous system and suggest the potential importance of eliciting HSV-specific mucosal CD8(+) CTL in HSV vaccine design.

Definition of amino acid residues on the epitope responsible for recognition by influenza A virus H1-specific, H2-specific, and H1- and H2-cross-reactive murine cytotoxic T-lymphocyte clones

We defined the epitopes recognized by three influenza A virus-specific, H-2Kd-restricted CD8(+) cytotoxic T-lymphocyte (CTL) clones: H1-specific clone A-12, H2-specific clone F-4, and H1- and H2-cross-reactive clone B7-B7. The A-12 and B7-B7 clones recognized the same peptide, which comprises amino acids 533 to 541 (IYSTVASSL) of A/PR/8 hemagglutinin (HA). The F-4 and B7-B7 clones both recognized the peptide which comprise amino acids 529 to 537 (IYATVAGSL) of A/Jap HA. Amino acids 533 to 541 of A/PR/8 HA are compatible with amino acids 529 to 537 of A/Jap HA. Amino acid S at positions 3 and 7 was responsible for recognition by H1-specific clone A-12, while amino acid G at position 7 was responsible for recognition by H2-specific clone F-4. Two conserved amino acids, T at position 4 and A at position 6, were responsible for recognition by H1-, and H2-cross-reactive clone B7-B7. These results indicate that a single nine-amino-acid region is recognized by HA-specific CTL clones of three different subtype specificities and that the amino acids responsible for the recognition by the CTL clones are different.

Antigen-specific tolerance induction and the immunotherapy of experimental autoimmune disease

Antigen-specific tolerance induction is the ultimate goal for specific immunotherapy of autoimmune diseases. Here we will discuss recent experiments designed to induce tolerance following mucosal administration of antigens in a mouse model of experimental autoimmune encephalomyelitis (EAE). We were unable to induce oral tolerance either with whole myelin, myelin basic protein (MBP) or the immunodominant peptide antigen. Oral tolerance was possible, however, with an analogue of the immunodominant peptide modified to increase its affinity for the restricting major histocompatibility complex (MHC) antigen. By contrast, intranasal deposition of peptide antigen proved highly effective for both prevention and treatment of EAE. Prevention of disease was directly related to the antigenic property of the peptide which, in itself, was related to affinity for MHC. Notably, administration of a single peptide was shown to inhibit disease involving multiple epitopes. We investigated the resulting bystander regulation by studying the cellular basis of peripheral tolerance in a transgenic model. These studies indicate that bystander regulation may be the consequence of selective cytokine secretion.

Allo- and self-restricted cytotoxic T lymphocytes against a peptide library: evidence for a functionally diverse allorestricted T cell repertoire

BALB/c-derived spleen cells were depleted of cytotoxic T lymphocytes (CTL) recognizing allogeneic (H2b) and TAP-negative cells followed by stimulation with the same cells loaded with a synthetic library binding to H2-Kb. The resulting CTL lines were found to differ widely in peptide specificity and to exhibit an avidity towards the library as that demonstrated for syngeneic CTL. These results demonstrate that positive selection in the context of a certain MHC molecule does not seem to be required for generating high-avidity TCR that are restricted by the same molecule. However, positive selection increases the frequency of such CTL. By raising T cell lines from a repertoire which did not undergo negative selection by the restriction element in question, it becomes possible to produce effective self-peptide/ MHC as well as nonself-peptide/MHC-specific CTL as tools for adoptive tumor immunotherapy.

Rescue of self-reactive B cells by provision of T cell help in vivo

We have previously demonstrated that antigen-specific T cell help can rescue mature Ig transgenic (Tg) hen egg lysozyme (HEL)-specific B cells from tolerance induction upon transfer into soluble HEL-expressing Tg hosts. Here we extend these findings by showing that T cell help could also rescue both immature and mature self-reactive B cells from rapid deletion in response to high-avidity membrane-bound HEL. Moreover, although short-lived anergic peripheral B cells that had matured in the presence of soluble self antigen could not be rescued by provision of T cell help, a proportion of immature anergic IgM+ IgD- CD23- B cells from the bone marrow of the same donors survived and proliferated when given help following transfer to a soluble or membrane HEL-expressing host. In other words, T cell help must be available relatively soon after the antigen signal to prevent induction of tolerance. Consistent with this interpretation, the stronger stimulus provided by membrane-bound antigen, which deletes immature B cells before they leave the bone marrow, did not afford an opportunity for T cell help to rescue tolerant immature bone marrow-derived B cells upon transfer in vivo. Nevertheless, these B cells were capable of responding to T cell help in vitro, which speaks against an immutable susceptibility of immature B cells to tolerance induction. Taken together, these data indicate that the strength of the antigen signal and availability of T cell help are the primary determinants of the fate of both immature and mature B cells, consistent with the model proposed by Bretscher and Cohn more than 25 years ago.

Rescue of self-reactive B cells by provision of T cell help in vivo

We have previously demonstrated that antigen-specific T cell help can rescue mature Ig transgenic (Tg) hen egg lysozyme (HEL)-specific B cells from tolerance induction upon transfer into soluble HEL-expressing Tg hosts. Here we extend these findings by showing that T cell help could also rescue both immature and mature self-reactive B cells from rapid deletion in response to high-avidity membrane-bound HEL. Moreover, although short-lived anergic peripheral B cells that had matured in the presence of soluble self antigen could not be rescued by provision of T cell help, a proportion of immature anergic IgM+ IgD- CD23- B cells from the bone marrow of the same donors survived and proliferated when given help following transfer to a soluble or membrane HEL-expressing host. In other words, T cell help must be available relatively soon after the antigen signal to prevent induction of tolerance. Consistent with this interpretation, the stronger stimulus provided by membrane-bound antigen, which deletes immature B cells before they leave the bone marrow, did not afford an opportunity for T cell help to rescue tolerant immature bone marrow-derived B cells upon transfer in vivo. Nevertheless, these B cells were capable of responding to T cell help in vitro, which speaks against an immutable susceptibility of immature B cells to tolerance induction. Taken together, these data indicate that the strength of the antigen signal and availability of T cell help are the primary determinants of the fate of both immature and mature B cells, consistent with the model proposed by Bretscher and Cohn more than 25 years ago.

Flexibility of the thyroiditogenic T cell repertoire for murine autoimmune thyroiditis in CD8-deficient (beta2m -/-) and T cell receptor Vbeta(c) congenic mice

In murine experimental autoimmune thyroiditis (EAT), previous studies have revealed a highly adaptable thyroiditogenic T cell repertoire which involves both CD4+ and CD8+ T cells in the susceptible H2k strain. To further test this flexibility, congenic B10.K mice lacking CD8+ T cells (B2m -/-) or harboring 70% T cell receptor (TCR) Vbeta gene deletions (Vbeta(c)) were immunized with mouse thyroglobulin (MTg) and evaluated for EAT 28 days later. All B2m -/- mice developed moderate antibodies to MTg, and thyroidal inflammation was comparable to B10.K mice, averaging 35-40%. Spleen cells (SC) from MTg-immunized mice were then injected into syngeneic recipients after stimulation in vitro with MTg or with conserved, thyroxine (T4)- or thyronine (T0)- containing 12mer peptides, hT4(5), hT0(2553), or hT4(2553), derived from the primary hormonogenic sites at position 5 or 2553 of human Tg. As previously shown in another H2k strain (CBA/J), all three peptides activated MTg-primed SC to transfer EAT in B10.K mice. hT4(5) and hT4(2553) were further tested in B10.K-Vbeta(c) and beta2m- B10.K mice. Both peptides expanded thyroiditogenic T cells in either strain, resulting in severe thyroiditis in syngeneic recipients. That EAT can develop in the absence of CD8+ T cells or in the presence of a severely restricted TCR repertoire underscores the remarkable flexibility of the thyroiditogenic T cell profile in the susceptible k haplotype.

Type II collagen in cartilage evokes peptide-specific tolerance and skews the immune response

T cell recognition of type II collagen (CII) is a crucial event in the induction of collagen-induced arthritis in the mouse. Several CII peptides have been shown to be of importance, dependent on which MHC haplotype the mouse carries. By sequencing the rat CII and comparing the sequence with mouse, human, bovine and chicken CII, we have found that the immunodominant peptides all differ at critical positions compared with the autologous mouse sequence. Transgenic expression of the immunodominant Aq-restricted heterologous CII 256-270 epitope inserted into type I collagen (TSC mice) or type II collagen (MMC-1 mice) led to epitope-specific tolerance. Immunization of TSC mice with chick CII led to arthritis and immune responses, dependent on the subdominant, Aq-restricted and chick-specific CII 190-200 epitope. Immunization of F1 mice, expressing both H-2q and H-2r as well as transgenic expression of the Aq-restricted CII 256-270 epitope in cartilage, with bovine CII, led to arthritis, dependent on the Ar-restricted, bovine-specific epitope CII 607-621. These data show that the immunodominance of CII recognition is directed towards heterologous determinants, and that T cells directed towards the corresponding autologous epitopes are tolerated without evidence of active suppression.

Role of a subdominant H-2Kd-restricted SV40 tumor antigen cytotoxic T lymphocyte epitope in tumor rejection

SV40-transformed mKSA cells (H-2d) readily induce progressively growing tumors in adult syngeneic BALB/c mice while expressing the full complement of H-2d MHC class I antigens. BALB/c mice previously immunized with SV40, soluble SV40 T antigen, or irradiated SV40-transformed syngeneic, allogeneic, or xenogeneic cells reject an mKSA tumor challenge even though these mice have been considered low- or nonresponders to T antigen due to difficulty in demonstrating SV40 T antigen-specific CTL. We have investigated the role of H-2d-restricted CTL in the rejection of SV40 tumors in BALB/c mice. Immunization of BALB/c mice with SV40 induced T antigen-specific CTL which were largely. H-2Ld-restricted. However, following repeated in vitro restimulation with mKSA cells, CTL emerged which recognized a subdominant H-2Kd-restricted epitope corresponding to T antigen residues 499-507. Immunization of BALB/c mice with a recombinant vaccinia virus expressing the T499-507 epitope provided partial protection against a challenge of syngeneic mKSA tumor cells and induced the generation of T499-507-specific CTL. These results indicate that a subdominant H-2Kd-restricted CTL epitope can participate in the rejection of SV40 tumors in BALB/c mice.

Mice expressing the E7 oncogene of HPV16 in epithelium show central tolerance, and evidence of peripheral anergising tolerance, to E7-encoded cytotoxic T-lymphocyte epitopes

In order to derive mice which expressed both the E7 open reading frame transgene of human papillomavirus type 16 in skin and MHC class 1 restriction elements for several E7-encoded cytotoxic T-lymphocyte (CTL) epitopes, K14.HPV16E7 mice which express E7 in basal keratinocytes were crossed to the F1 generation with A2.1 Kb transgenic mice which express the MHC binding cleft domains of human HLA A*0201, and murine H-2b. F1 mice (denoted K14E7 x A2.1) expressed E7 in the thymus at least as early as 2-5 days before birth. Immunisation of FVB x A2.1 control mice (transgenic for HLA A*0201 and H-2b but not for E7), with two HLA A*0201-restricted epitopes of E7 and one H-2b-restricted CTL epitope of E7, gave strong primary CTL responses recognising epitope-pulsed or constitutively E7-expressing syngeneic target cells. In contrast, in immunised K14E7 x A2.1 mice, the CTL responses to the H-2b epitope and one of the HLA A*0201 CTL epitopes were strongly down-regulated, and to the other HLA A*0201 epitope, completely abolished, as demonstrated by percentage specific killing by bulk splenocyte cultures in cytotoxicity assays, and by CTL precursor frequency analysis. In thymus-transplanted bone marrow radiation chimeras in which the immune system of K14E7 x A2.1 mice was replaced by a FVB x A2.1 immune system, specific immunisation did not result in reemergence of strong E7-directed CTL responses. In agreement with these in vitro findings, specific immunisation failed to significantly alter the course of E7-associated tumour development in K14E7 x A2.1 mice. These data are consistent with a model of central deletional CTL tolerance to E7-encoded epitopes recognised in the context of two distinct MHC class 1 restriction elements, and with the possibility of peripheral T-cell anergy maintained by expression of E7 in the skin.

Interleukin 12 gene therapy of MHC-negative murine melanoma metastases

Immunological gene therapy of cancer relies heavily on the activation of T cells, but tumors with defects in MHC gene expression are not recognized by MHC-restricted T cells. To investigate the potential of cytokine genes for the therapy of MHC-negative tumors, we transduced B78H1, a class I-negative murine melanoma clone, with a polycistronic vector carrying murine interleukin (IL)-12 genes. The clones studied produced 400-25,000 pg/ml IL-12; their in vitro growth properties were similar to those of parental cells. A complete inhibition of growth was observed in vivo both after s.c. and i.v. administration of all IL-12 clones. IL-12-transduced cells were also used as a therapeutic vaccine in mice bearing micrometastases by nontransduced parental cells. A significant (80-90%) reduction in the number of lung nodules was obtained. Immunohistochemical analysis and studies in immunocompromised hosts showed that T cells and natural killer cells had a significant role in the elimination of IL-12-releasing cells. In situ hybridization with cytokine probes detected a strong increase in the proportion of leukocytes positive for IFN-gamma, tumor necrosis factor alpha, IL-1beta, and IFN-inducible protein 10 at the site of rejection of IL-12-engineered tumor cells. However, it was clear that the loss of in vivo growth was also due to T-cell- and natural killer cell-independent factors, possibly related to the antiangiogenic properties of IL-12. In conclusion, tumor therapy based on IL-12 gene transduction was effective on a MHC-negative metastatic tumor, suggesting a possible application to MHC-defective human neoplasms.

A structure-based approach to designing synthetic CD8alpha peptides that can inhibit cytotoxic T-lymphocyte responses

CD8 molecules function as co-receptors on cytotoxic T lymphocytes (CTLs), interacting with a nonpolymorphic region of the major histocompatibility complex (MHC) class I a3 domain on antigen-presenting cells. Analogues were designed from a structural model of the mouse CD8a molecule to identify surfaces involved in CD8 function. Peptides were screened for in vitro biological activity on alloreactive CTLs, and analogue SC4 (p54-59) was found to be inhibitory during both the generation and effector stages. SC4 was also able to significantly prolong skin allograft survival across a MHC class I barrier. Thus, such CD8 analogues may have therapeutic potential as immunoregulators of CTL immune responses.

Analysis of expression of lymphocyte homing-related adhesion molecules in ALY mice deficient in lymph nodes and Peyer's patches

The aly, alymphoplasia, is an autosomal recessive mutation in mice of an unknown etiology, which induces total aplasia of lymph nodes and Peyer's patches. We hypothesized that the lack of lymphoid tissue may be due to abnormalities of lymphocyte traffic into these tissues. Therefore, we analyzed the expression of various adhesion molecules associated with lymphocyte homing. Among the adhesion molecules examined, all were normally expressed except the mucosal addressin MAdCAM-1. In aly/aly mice MAdCAM-1 was absent in the spleen at mRNA and protein levels, but was normally expressed in the intestinal venules. The FISH analysis and linkage analysis using microsatellite markers demonstrated that the MAdCAM-1 gene is located on chromosome 10, indicating that MAdCAM-1 is not encoded by the aly gene, which is located on chromosome 11. Our results indicate that the aberrant expression of MAdCAM-1 is not the direct cause of aly mutation but rather a secondary defect.

T cell tolerance to kappa light chain (L kappa): identification of a naturally processed self-C kappa-peptidic region by specific CD4+ T cell hybridomas obtained in L kappa-deficient mice

In contrast to H-2d kappa light chain-deficient mice (kappa-/-), BALB/c (kappa+/+) mice fail to respond to kappa light chains (L kappa). This suggests that C kappa-specific T cells are tolerant to this self-antigen in kappa+/+ mice. To get insights into the cellular and molecular basis of this tolerance, we first characterized the presented L kappa-derived C kappa-peptidic region(s). Among a library of overlapping peptides spanning the whole C kappa sequence, only three consecutive peptides are recognized by CD4+ T cell hybridomas obtained in L kappa-immunized kappa-/- mice. This C kappa-peptidic region, which is also the only one containing the I-Ed-binding consensus motif, is immunogenic since it is able to prime lymph node cells of kappa-/- mice to subsequent in vitro proliferative response to either L kappa or kappa+/+ APC. Conversely, no kappa+/+ T cell proliferation is observed under the same conditions. Activation of our hybridomas by cells from central and peripheral lymphoid tissues reveals that this C kappa region is naturally expressed on BALB/c kappa+/+ APC. In addition to B cells, macrophages and dendritic cells are able to present this region. Taken together our data suggest that the described self-C kappa region is implicated in the C kappa-specific CD4+ T cell tolerization in BALB/c mice.

Priming of cytotoxic T lymphocytes by DNA vaccines: requirement for professional antigen presenting cells and evidence for antigen transfer from myocytes

BACKGROUND

MHC class I molecule-restricted cytotoxic T-lymphocyte (CTL) responses are induced following either intramuscular (i.m.) injection of a DNA plasmid encoding influenza virus nucleoprotein (NP) or transplantation of myoblasts stably transfected with the NP gene, the latter indicating that synthesis of NP by myocytes in vivo is sufficient to induce CTL. The present study was designed to investigate the role of muscle cells and involvement of professional antigen-presenting cells (APCs) in priming CTL responses following DNA vaccination.

MATERIALS AND METHODS

Parent-->F1 bone marrow (BM) chimeric mice were generated whose somatic cells include muscle cells bearing both parental MHC haplotypes, while their professional APCs express only the donor MHC haplotypes.

RESULTS AND CONCLUSIONS

Upon injection of NP DNA, or after infection with influenza virus, CTL responses generated in the chimeras were restricted to the donor MHC haplotype. Thus cells of BM lineage were definitively shown to be responsible for priming such CTL responses after infection or DNA immunization. Moreover, expression of antigen by muscle cells in BM chimeric mice after myoblast transplantation is sufficient to induce CTL restricted only by the MHC haplotype of the donor BM. This indicates that transfer of antigen from myocytes to professional APCs can occur, thus obviating a requirement for direct transfection of BM-derived cells.

Peptide mimicry of carbohydrate epitopes on human immunodeficiency virus

Cancer-related, mucin-type carbohydrate epitopes, principally mannose and sialo-syl residues, are expressed on the envelope protein gp 160 of the human immunodeficiency virus (HIV). Anticarbohydrate antibodies directed toward these and other carbohydrate epitopes are known to neutralize HIV-1 infection by cell-free virus. Carbohydrates, however, being T cell-independent antigens, typically elicit diminished immune responses. To overcome this potential draw back, we have examined the ability of peptides that mimic such epitopes to elicit immune responses that cross-react with carbohydrate structures. We report that mouse polyclonal antisera generated against peptides that mimic mucin-related carbohydrate epitopes have anti-HIV-1 activity. Generation of antibodies was not lr-gene restricted, as at least two different strains of mice. Balb/c (H-2d) and C57Bl/6 (H-2b), responded equally to the peptides. The antipeptide sera displayed neutralizing activity against HIV-I/MN and HIV-I/3B viral strains. This neutralization was as good as human anti-HIV sera. These results indicate that peptide mimics of carbohydrates provide a novel strategy for the further development of reagents that elicit immune responses to carbohydrate epitopes associated with many infectious organisms and tumor cells.

Cutaneous delayed type hypersensitivity in SCID mice adoptively transferred with lymphocytes is B cell independent and H-2 restricted

Severe combined immunodeficiency (SCID) mice are largely devoid of functional T and B lymphocytes but have normal antigen presenting cell (APC) capacity. The authors have examined the requirements for cutaneous delayed type hypersensitivity (DTH) in SCID recipients by i.p. transfer of freshly isolated naive mature. T cells or non-fractionated spleen cells of H-2 compatible or incompatible origin. Recipient SCID mice were epicutaneously sensitized with oxazolone (OXA) within 24 h after cell transfer. SCID mice injected with as few as 10(5) H-2 compatible BALB/c (H-2d) spleen cells were able to mount DTH ear swelling reaction upon sensitization and challenge with OXA. Non-fractionated spleen cells from H-2 incompatible B6 or NZW mice were also able to restore DTH capacity in SCID recipients. However, when thymocytes were transferred, only donor mice expressing H-2d, but not H-2b and H-2z, haplotype restored DTH reactivity. Serum levels of IgM and IgM anti-OXA antibodies in SCID mice 27 days post-transfer with 10(7) BALB/c spleen cells were similar to that of intact donor mice. In contrast, specific antibodies of IgG isotype were approximately only one-tenth of that found in BALB/c controls. The results of this study show that for the development of cutaneous DTH, in SCID mice transferred with T cells, H-2 restricted APC-T cell interaction is required, whereas B cells are not mandatory. Also, SCID mice transferred with splenocytes show signs of defect immunoglobulin switch function. The authors believe that this model of DTH will be useful in delineating the effects of immunomodulatory substances in vivo on distinct host versus donor cell populations.

Peptide-specific killing of antigen-presenting cells by a recombinant antibody-toxin fusion protein targeted to major histocompatibility complex/peptide class I complexes with T cell receptor-like specificity

Specificity in the immune system is dictated and regulated by specific recognition of peptide/major histocompatibility complex (MHC) complexes by the T cell receptor. Such peptide/MHC complexes are a desirable target for novel approaches in immunotherapy because of their highly restricted fine specificity. Recently, phage display was used to isolate an antibody that has T cell receptor-like specificity. It recognizes mouse MHC class I H-2Kk molecules complexed with a H-2Kk-restricted influenza virus-derived hemagglutinin peptide (Ha255-262) but does not bind to class I H-2Kk alone, peptide alone, or H-2Kk complexed with other peptides. We have used this antibody to make a recombinant antibody-toxin fusion protein (immunotoxin) and show herein that it specifically kills antigen-presenting cells in a peptide-dependent manner and with T cell receptor-like specificity. We find a striking correlation between the fine specificity of binding of the antibody and the cytotoxic activity of the recombinant immunotoxin. We also show specific killing of influenza virus-infected target cells. The results suggest that it should be possible to develop novel immunotherapeutic strategies against human cancer by making recombinant antibodies that will recognize cancer-related peptides complexed with MHC class I molecules on the surface of cancer cells and using these to deliver toxins, radioisotopes, or cytotoxic drugs to the cancer cells.

Production of a T-cell clone which reacts with membrane proteins of Acholeplasma laidlawii

The role of cellular immunity in mycoplasma infection is not completely understood. In this study, we established mycoplasma-specific T-cell clones to evaluate cellular immunity in mycoplasma infection. We developed a T-cell clone (G-10) which was stimulated with Acholeplasma laidlawii. The T-cell clone G-10, CD4+ and T-cell receptor (TCR) alpha beta- recognized the 42- and 65-kilodalton (kDa) membrane proteins of A. laidlawii and responded to A. hippikon. Hence, the application of mycoplasma-specific T cells such as G-10 in animal models may allow the assessment of cellular immune response to mycoplasma infection.

THE EXPRESSION OF HISTOCOMPATIBILITY ANTIGENS ON CELLULAR AND SUBCELLULAR MEMBRANES

The mouse isoantigens determined at the major histocompatibility locus known as H-2 have been found to be closely associated with the cellular surface membranes, with the membranes of the endoplasmic reticulum, and probably with those of the lysosomes as well. Mitochondrial membranes, on the other hand, show little or no H-2 antigen activity. Membrane material prepared from certain tissues, including brain and muscle, have no detectable H-2 antigenic activity. Evidence is presented which indicates that all of the H-2 antigens of the genome are expressed as a unit, supporting the hypothesis that the complex H-2 genetic locus consists of a single cistron. It is postulated that these histocompatibility antigens form some structural or functional unit in the membranes of cells.

Hierarchical self-tolerance to T cell determinants within the ubiquitous nuclear self-antigen La (SS-B) permits induction of systemic autoimmunity in normal mice

Systemic autoimmune diseases are frequently associated with clustering of high titer autoantibody responses towards nuclear self-antigens. Little is known, however, about the extent of immune tolerance to the target nuclear antigens or the events leading to the complex autoantibody responses that are characteristic of systemic autoimmunity. To address these issues, we have examined the mouse immune response to La autoantigen (mLa) and the homologous human La antigen (hLa), which are components of the La(SS-B)/Ro(SS-A) ribonucleoprotein (RNP) complex targeted in systemic lupus erythematosus and primary Sjögren's syndrome. The findings reveal the presence of hierarchical T cell tolerance involving multiple autodeterminants within the La autoantigen expressed by normal H-2k and H-2a mice. At one end of this spectrum, there was no detectable T or B cell autoimmunity observed in mice that were immunized with the immunodominant mLa287-301 determinant, which differed by a single residue in its core sequence from the homologous but highly immunogenic human La288-302 determinant. Interestingly, the mLa287-301 peptide acted as an altered peptide ligand that specifically antagonized the activation of an hLa288-302-specific T cell hybridoma. In contrast to the tolerogenic mLa287-301 determinant, a range of autoimmune potential was identified among poorly tolerizing, subdominant self-peptides present within mouse La autoantigen. Notably, immunization of normal mice with the autologous subdominant La25-44 and La106-129 determinants resulted in limited or no detectable autoantibody response. In contrast, immunization with the subdominant mouse La13-30 determinant induced a proliferative T cell response associated with the appearance of specific autoantibodies recognizing multiple intrastructural (La) and intermolecular components (Ro) of the murine La/Ro RNP. The findings suggest how diversified autoimmunity might follow initiation of immunity to simple peptide mimics of poorly tolerogenic determinants that are present within ubiquitous self-antigens.