Impaired H-2 expression in B16 melanoma variants

We studied the expression of H-2b alloantigens in three different B16 melanoma lines cultures in vitro. Cell lines were B16-F1 and two cell cultures (named B16-A and B16-B) newly derived from two different in vivo sublines of B16 melanoma. The assays used were in vivo tumour growth in allogeneic (BALB/c and B10.BR) as compared to syngeneic mice, in vitro cell-mediated cytotoxicity by anti-H-2b immune lymphocytes and absorption of anti-H-2b antisera activity. The B16-F1 line was able to efficiently kill allogeneic hosts, could not be lysed by anti-H-2b cytotoxic effectors and did not express any serologically detectable amount of H-2b alloantigens. The B16-A line was H-2 positive during the early in vitro passages, then, at the 8th-10th passages, it acquired the capacity to kill allogeneic hosts, lost the sensitivity to anti-H-2b cytotoxic effectors and the H-2Kb antigens became undetectable The expression of H-2Db was reduced, although at a lower degree. Similar data were obtained with B16-B cells, which after 10 in vitro passages grew and killed allogeneic hosts, showed a decreased sensitivity to cytotoxic anti-H-2b effectors and a very low expression of the K region antigens. The results indicate that H-2 expression is altered in B16 melanoma lines and this may influence the different metastatic capacity of such cells.     

Interferon-mediated enhancement of metastasis. Are MHC antigens involved?

The relationship between major histocompatibility complex (MHC) antigens and metastasis was investigated on B16 melanoma variants. B16 cell lines express low amounts of murine MHC (H-2) antigens. A high expression can be induced in line B16-A by in vitro treatment with immune interferon (IFN-gamma) or by in vivo transplant in allogeneic mice. The increase of H-2 antigens correlated with an enhancement of lung colonization in young syngeneic mice. The higher metastatic capacity of B16-A cells with induced high levels of H-2 antigens was observed also in adult mice and in young mice pretreated with cyclophosphamide. These results were confirmed investigating the behaviour of a mutant B16 clone (B78H1) which was selectively resistant to the H-2-inducing action of IFN-gamma: lung colonization ability was not increased by IFN pretreatment. The study of variants derived from individual B16-A lung colonies revealed a wide range of H-2 levels. Variants with a low expression had a low colonization ability; one out of two variants with a high H-2 expression also was poorly colonizing. IFN-gamma-mediated H-2 expression appeared to act as an enhancer, rather than a determinant of B16 metastatic capacity.     

Original H-2d and alien H-2k-like antigens of a BALB/c fibrosarcoma as defined by in vitro and in vivo studies of cell-mediated immunity

The present study examines the immunosensitivity and the immunogenicity of both original H-2^d and alien H-2^k-like antigens of the BALB/c (H-2^d) fibrosarcoma C-1 as detected by in vitro and in vivo cell-mediated cytotoxicity (CMC) assays. It was found that ⁵¹Cr-labeled C-1 cells were lysed in vitro by C 57 BL/6 anti-H-2^d lymphocytes. The specificity of this reaction was shown by cold inhibition experiments in which the anti-H-2^d cytotoxic activity on YC8 (H-2^d) targets was inhibited by unlabeled YC8 or C-1 but not by C3UR11 (H-2^k) tumor cells. Both D^d- and K^d-encoded antigens were recognized by appropriate cytotoxic effectors. The immunogenicity of H-2^d antigens of C-1 was revealed by the ability of C 57 BL/6 anti-C-1 lymphocytes to lyse YC8 targets. The expression of H-2^k-like alien alloantigens on C-1 was indicated by the finding that anti-H-2^k cytotoxic T lymphocytes (CTL), generated by culturing BALB/c spleen cells immune to BALB.K (H-2^k), C3Hf (H-2^k) or A (H-2^a = H-2^k/d) tissues with the cells of the same strain used for immunization, lysed C-1 targets. The cytotoxicity of these anti-H-2^k CTL against C 3 UR11 (H-2^k) targets could be specifically inhibited by cold C 3 UR 11 or C-1 cells but not by two other BALB/c tumors. Using recombinant H-2-congenic mice, it was shown that both D^k and K^k antigens were recognized by CTL on C-1 cells. The immunogenicity of the H-2^k-like antigens, however, could not be detected in vitro. In fact, effector spleen cells from BALB/c mice immune to C-1 did not develop any detectable cytotoxicity against C 3 UR 11 targets as assayed either by a direct in vitro test or after in vitro restimulation with C-1 sarcoma cells. A similar experimental design was adopted in Winn assays carried out by mixing spleen cells of BALB/c immune mice with either C-1 or C3 UR 11 targets and injecting the mixtures in BALB/c or hybrid recipients. These in vivo tests revealed the presence of both H-2^d (K^d and D^d) and H-2^k-like (K^k and D^k) antigens on C-1. At variance with the in vitro CMC assays, however, the Winn assay also detected the immunogenicity of the H-2^k alien antigens, since BALB/c anti-C-1 spleen cells were able to significantly reduce the growth of C 3 UR 11 lymphoma cells in (BALB/c × C 3 Hf)F₁ hosts.     

In vivo reexpression of H-2 antigens in B16 melanoma cells

We have previously shown that B16-A (H-2b) murine melanoma cells, when cultured in vitro for more than ten passages, have an undetectable or reduced expression of H-2Kb and Db antigens, respectively. We have now studied the possibility to restore H-2 expression (measured by quantitative antisera absorption) in B16-A cells either by a limited (30 days) period of in vivo growth or by treatment with immune interferon. In vivo transplants in allogeneic H-2k or H-2d mice and in H-2-compatible but Mls and multiple non-H-2 loci incompatible mice restored the normal expression of Kb and Db antigens. Cells obtained from tumors grown in syngeneic or in minor histocompatibility antigens-allogeneic mice showed only a weak increase in Db antigens. Such induction of H-2 expression appears to be mediated by the host's immune system, since (1) cells obtained from tumors grown in allogeneic BALB/c nude mice expressed much lower levels of H-2 antigens than those from tumors grown in normal BALB/c mice, and (2) it was possible to induce H-2 expression by growing B16 cells in syngeneic C57Bl/6 mice previously allostimulated with unrelated BALB/c tumor. In vitro treatment with immune interferon restored the expression of both Kb and Db antigens. We hypothesize that H-2 reexpression on B16 cells grown in allogeneic hosts could take place via the nonspecific components of the immune response, such as immune interferon.     

Growth and metastasis in allogeneic hosts. Lack of H-2-negative or somatic hybrid variant selection

In vitro cultured B16 melanoma cells, which were previously found to have an impaired expression of H-2Kb and Db (as evaluated by antisera absorption assay), were used to study growth and metastasis in allogeneic mice in relation to H-2 expression. The possible emergence of somatic hybrids with host cells was also examined. B16-A cells grown subcutaneously in allogeneic BALB/c mice (H-2d) did not show a lack of H-2b expression, nor the acquirement of H-2d antigens was found. Spontaneous lung metastases were found in about 30% of BALB/c mice with progressing B16 tumor. Single lung metastases showed higher H-2b levels than cells from the respective tumors, and did not express host H-2 antigens. Tumor take was concomitant to the rise of an anti-H-2b humoral response: disease outcome was independent from the serum titer. B16-A cells injected intravenously in BALB/c mice gave rise to lung colonies; different colonies showed a wide range of H-2b antigens levels and no H-2d expression. Lung colonization capacity in normal allogeneic BALB/c mice was significantly higher than in syngeneic C57BL/6 mice. Both syngeneic and allogeneic mice, when pretreated with cyclophosphamide (CY) to reduce natural killer cell activity, showed a significant increase in lung colonization by B16-A cells. CY-treated C57BL/6 mice showed significantly higher numbers of lung colonies than CY-treated BALB/c mice. In conclusion, B16 growth and metastasis in the allogeneic environment do not seem to be determined by a selection of H-2-negative variants or by the emergence of somatic hybrids with host cells.     

ORIGINAL H-2d AND FOREIGN H - 2k - LIKE ANTIGENS ARE INDEPENDENT ENTITIES ON A CHEMICALLY INDUCED SARCOMA

We have previously shown that a methylcholanthrene-induced sarcoma of BALB/c strain (C-1) expressed, in addition to its original H-2^d antigens, foreign H-2^k-like determinants. In the present study the relationship between H-2^d and H-2^k-like antigens was examined by in vitro and in vivo assays. Cultured tumour cells were exposed in the cold to either a monospecific (D-23, D-25, D-1) or polyspecific (BALB/c anti-C3Hf) alloantiserum directed to H-2^k specificities and then used to absorb the cytotoxic activity of either monospecific (D-31) or a polyspecific (C3Hf anti-BALB/c) alloantisera to H-2^d antigens (blocking test). The opposite was also done, i.e. tumour cells were coated with anti-H-2^d sera and used to absorb the cytotoxicity of anti-H-2^k sera. No reciprocal interference was found between the two H-2-different antigens in the absorption of related alloantisera. Suspensions of irradiated C-1 tumour cells were exposed in vitro to either anti-H-2^d or anti-H-2^k antisera and then used to immunize either syngeneic BALB/c or allogeneic C3Hf mice. The coating of immunizing neoplastic cells with BALB/c anti-C3Hf serum prevented anti-C3Hf (anti-H-2^k) antibody production in BALB/c mice without affecting anti-BALB/c (anti-H-2^d) antibody development in C3Hf animals; coating of H-2^d antigens on tumour cells strongly reduced anti-BALB/c but not anti-C3Hf antibody production. Both in vitro and in vivo experiments indicated that foreign H-2^k-like determinants are physically separated from the wild H-2^d antigens on the C-1 sarcoma cells.     

Enhancement of experimental metastatic ability by tumor necrosis factor-alpha alone or in combination with interferon-gamma

The effects of recombinant tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) on B16 mouse melanoma experimental metastatic ability and major histocompatibility complex (H-2^b) antigens expression were studied. B16 cells exposed in vitro to TNF-alpha had an increased H-2 expression and were more metastatic than untreated cells. The simultaneous treatment with TNF-alpha and IFN-gamma amplified the enhancement of experimental metastasis and all other effects obtained with TNF-alpha alone. The B16 clone B78H1, selectively resistant to H-2 induction and to enhancement of metastatic ability by IFN-gamma, was not affected by treatment with TNF-alpha and with TNF-alpha + IFN-gamma. These findings contribute to a better understanding of the pleiotropic effects of TNF, some of which can have opposing actions in the complex tumor-host relationships.[/p]     

Control of metastatic properties of BL6 melanoma cells by H-2Kb gene: immunological and nonimmunological mechanisms

The effect of class I H-2 antigen expression on the metastatic properties of BL6 melanoma cells was investigated. The BL6-8 clone isolated from the highly metastatic BL6 melanoma did not express H-2K b gene. Following transfection with the H-2K^b gene, BL6-8 cells displayed a low metastatic potential in the immunocompetent as well as immunosuppressed (X-irradiated) or triple-immunodeficient mice with impaired T, B and natural killer (NK) cells function. The expression of H-2K^b gene and the low metastatic ability of transfected BL6 melanoma cells were associated with appearance of cell membrane soybean agglutinin (SBA) and Griffonia simplicifolia 1B₄ (GS1B₄) lectin-binding carbohydrataes. These alterations in cell surface carbohydrates were found to be a result of reduction in sialylation of SBA binding sites and upregulation of the 1.3 galactosyltransferase (1.3GT) gene. To assess the importance of H-2K^b-induced alterations in cell surface carbohydrates for metastasis formation, BL6-8 melanoma cells were transfected with H-2K^b gene without neo^r gene cotransfection and selected for adherence to SBA-lectin-conjugated agarose beads. The transfected clones that expressed SBA and GS1B₄ lectin-binding carbohydrates were low metastatic. Further analysis of these clones showed that presence of SBA and GS1B₄ lectin-binding carbohydrates rather than expression of H-2K^b molecules per se might be responsible for low metastatic potentials of H-2K^b-transfected cells in the immunocompromized mice. Studies of the possible mechanisms responsible for low metastatic ability of H-2K^b-transfected melanoma cells revealed that these cells displayed a reduced ability to adhere to murine pulmonary endothelial cells as well as to laminin and collagen IV. We hypothesized that the observed nonimmunological effects of H-2K^b gene in BL6 melanoma cells is a result of an interaction between the H-2K^b gene and B16 melanoma-specific ecotropic retrovirus. It results in inhibition of this retrovirus production with consecutive alteration in the expression of cellular genes controlling cell surface glycosylation and adhesion properties essential for the metastatic phenotype of BL6 melanoma.     

Ir gene expression on T cells: Effect of a monoclonal antibody directed against I region-controlled determinants on T cells

A monoclonal antibody directed at an I region-controlled epitope uniquely expressed on T cells (Iat) was studied for its in vivo effect on the antibody response under the control of an Ir gene. The antibody was produced by a hybridoma made from A.TH spleen cells immune to A.TL (anti-I^k), that was selected for its reactivity with T but not B cells and macrophages, and thus was designated as anti-Iat^k. The injection of this anti-Iat^k into H-2^k, H-2^b and H-2^k×bF₁ mice resulted in the suppression of antibody response to poly-L-(His,Glu)-poly-D,L -Ala–poly-L -Lys [(H,G)-A–L] in H-2^k and F₁ mice but not that to poly-L -(Tyr,Glu)-poly-D,L -Ala–poly-L -Lys [(T,G)-A–L] both in H-2^b and F₁ mice. The adoptive cell transfer of the combinations of anti-Iat^k-or normal mouse serum-treated T and B cells into irradiated hosts demonstrated that anti-Iat^k primarily affected (H,G)-A–L-specific helper T cells but not B cells and macrophages, resulting in the specific elimination of the antibody response. Suppressor T cells were not induced by the treatment with anti-Iat^k. The antibody specifically eliminated the (H,G)-A–L-specific but not (T,G)-A–L-specific helper T cells in F₁ spleen cells that had been primed with both (H,G)-A–L and (T,G)-A–L. The results indicated that anti-Iat^k affected the H-2^k-associated Ir gene function born by T cells but not by antigen-presenting cells, which was expressed on F₁ helper T cells with apparent exclusion of the other allele, and implied that the Iat antigen on helper T cells is one of the sites of expression of Ir genes.     

Polymorphism of a Qa-1-associated antigen defined by cytotoxic T cells. I. Qed-1a and Qed-1d

Tla^d mice have a distinct Qed-1 allele, Qed-1^d. Its product is detected by cytotoxic T cells raised in C57BW6 (H-2^b, Tla^b) mice against cells from a new recombinant, B6-TL.123⁺ (H-2^b, Tla^d/b). Qed-1^d is also found on cells from B10.M, A.CA and B10.STC90 mice. It cross-reacts weakly with Qed-1^b. (C57BL/6 X BALB/c) F₁ anti-B10. A (SR) effectors discriminate Qed-1^a and Qed-1^d, while C3H/HeJ anti-B10. BR effectors cross-react extensively. CB6F₁ anti-5R effector cells also discriminate between the Qed-1 antigens of B6-Tla^a (H-2^b, Tla^a) and those of B10. BR and other H-2k, Tla^a strains.     

H-2Kb transfection of B16 melanoma cells results in reduced tumourigenicity and metastatic competence

The metastatic B16 mouse melanoma shows a low cell surface expression of H-2Kb and H-2Db class I antigens on cells of both the high-metastatic line B16-F10 and the low-metastatic line B16-F1. Similarly, newly generated clones of these lines, having different metastatic properties, all express low levels of major histocompatibility antigens. One of these clones, the high-metastatic F10.9, was transfected with H-2Kb genes to generate H-2Kb-expressing transfectants. The resulting clones showed reduced tumourigenicity and a low metastatic phenotype. Unlike the parental cells, H-2Kb-positive transfectants are potent inducers and sensitive targets of H-2Kb-restricted syngeneic cytotoxic T cells. Immunization of mice with H-2Kb-positive transfectants conferred protection against a subsequent challenge with Kb-positive transfectants but had only a small effect on growth and metastatic spread of parental cells.     

Major histocompatibility complex class I presentation of exogenously acquired minor alloantigens initiates skin allograft rejection

Major histocompatibility complex (MHC) class I molecules present peptides from endogenous proteins. However, in some cases class I-restricted peptides can also derive from exogenous antigens. This MHC class I exogenous presentation could be involved in minor histocompatibility antigen (mHAg)-disparate allograft rejection when donor alloantigens are not expressed in graft antigen-presenting cells (APC) that initiate the rejection mechanism. Here we addressed this question by using a skin graft experimental model where donors (H-2^b or H-2^d Tgβ-gal mice) expressed the mHAg like β-galactosidase (β-gal) in keratinocytes but not in Langerhans' cells (LC) which have an APC function. Rejection of Tgβ-gal skin by a β-gal-specific CD8 cytotoxic T lymphocyte (CTL) effector mechanism should require presentation by donor and/or recipient LC of MHC class I-restricted peptides of exogenous β-gal shed by keratinocytes. Indeed, our results showed that 1) H-2^b Tgβ-gal skin was rejected by H-2^bxs and H-2^bxd recipients; 2) rejection was mediated by β-gal-specific CD8⁺ CTL effectors; and 3) H-2^bxd mice having rejected H-2^b Tgβ-gal skin generated β-gal-specific CTL restricted by H-2^b and H-2^d class I molecules and rejected subsequently grafted H-2^d Tgβ-gal skin in an accelerated fashion, demonstrating that recipient LC have presented exogenous β-gal-derived MHC class I epitopes. These results lead to the conclusion that MHC class I exogenous presentation of donor mHAg can initiate allograft rejection.     

The specificity of H-2-restricted cytotoxic T lymphocytes directed to AKR/Gross leukemia virus-induced tumors I. Isolation of a selectively resistant variant tumor subclone

The AKR.H-2^bSL1 tumor cell line is susceptible to H-2K^b-restricted cytotoxic T lymphocytes (CTL) directed against the subclass of AKR endogenous leukemia virus-induced tumors that express the Gross cell surface antigen (anti-AKR/Gross virus CTL). A variant subclone (cl.18-5) of AKR.H-2^bSL1 was isolated, whose susceptibility to lysis by conventional or cloned lines of anti-AKR/Gross virus CTL was approximately 5% or less than that of the parental tumor. The cl.18-5 variant was also ineffective when used as an in vivo priming cell or an in vitro stimulator cell in the generation of anti-AKR/Gross virus CTL or as an unlabeled target cell in competitive inhibition assays. These results implied that the failure of cl.18-5 to be lysed was due to a lack of recognition by the CTL. In contrast, cl.18-5 was able to be lysed by and stimulate the generation of predominantly H-2D^b-restricted CTL with apparent specificity for AKR minor histocompatibility antigens. The variant line was also about as susceptible as the parental AKR.H-2^bSL1 line to both allogeneic CTL and to H-2K^b-restricted, TNP-specific CTL. Thus, the lack of recognition of cl.18-5 by anti-AKR/Gross virus CTL did not appear to be due to a failure to express functional H-2 products or to a generalized insusceptibility to H-2-restricted CTL. Rather, cl.18-5 appeared to be a selective variant and a useful probe for studying the specificity of anti-AKR/Gross virus CTL.     

Presentation of a horse cytochrome c peptide by multiple H-2b class I major histocompatibility complex (MHC) molecules to C57BL/6- and bm1-derived cytotoxic T lymphocytes: Presence of a single MHC anchor residue may confer efficient peptide-specific CTL recognition

In this study the immunogenic tryptic fragment from a horse cytochrome c (cyt c) digest recognized by cytotoxic T lymphocytes (CTL), induced by in vitro peptide stimulation from C57BL/6 (B6) and mutant B6.C-H-2^bm1 (bm1) mice is identified. An identical sequence, p40—53, is recognized by CTL from both B6 and bm1 mice. In addition, both B6 and bm1 cloned CTL lines display unusual major histocompatibility complex (MHC) class I-restricted recognition of this peptide in that they respond to it in the context of H-2K^b, H-2D^b, and H-2K^bm1 class I molecules, although the sequence lacks the usual structural K^b and D^b peptide-binding motifs. Truncated analogues which resemble the lengths of naturally processed MHC class I-presented peptides, confer reactivity for B6 and bm1 CTL against EL4 (H-2^b) targets as well as the L cell transfectants, L + K^b, L + D^b, and L + K^bm1. The antigenic peptide with the greatest potency is p41—49, which appears to be generated by angiotensin converting enzyme cleavage of the full-length p40—53 tryptic peptide. The minimum antigenic peptide recognized by both B6 and bm1 CTL, and which targets lysis on each of the transfectants, is the hexamer p43—48 peptide from horse cyt c. Residues Pro⁴⁴ and Thr⁴⁷, which occupy polymorphic positions with respect to other species-variant cyt c molecules, influence recognition of these peptides differently for the B6 and bm1 CTL. The ability of H-2K^b, H-2D^b, and mutant H-2K^bm1 class I molecules to present the same peptide to a single cloned CTL is discussed in the context of current knowledge of peptide anchor residues and side chain-specific binding pockets in the MHC class I peptide-binding site.     

Vaccination with cytotoxic T lymphocyte epitope-containing peptide protects against a tumor induced by human papillomavirus type 16-transformed cells

Cytotoxic T lymphocyte (CTL) peptide epitopes can be used for immunization of mice against lethal virus infection. To study whether this approach can be successful against virus-induced tumors we generated a B6 (H-2^b) tumorigenic cell line transformed by human papillomavirus (HPV). This virus is detected in over 90% of all human cervical cancers. To identify vaccine candidates, we generated a set of 240 overlapping peptides derived from the HPV type 16 (HPV16) oncogenes E6 and E7. These peptides were tested for their ability to bind H-2K^b and H-2D^b MHC class I molecules. Binding peptides were compared with the presently known peptide-binding motifs for H-2K^b and H-2D^b and the predictive value of these motifs is shortly discussed. The high-affinity H-2D^b-binding peptide and putative CTL epitope E₇ 49-57 (RAHYNIVTF) was used in vaccination studies against HPV 16-transformed tumor cells. Immunization with peptide E₇ 49-57 rendered mice insensitive to a subsequent challenge with HPV 16-transformed tumor cells in vivo, and induced a CTL response which lysed the tumor cells in vitro.     

The mechanism of specific prolongation of class I-mismatched skin grafts induced by retroviral gene therapy

In the present study, we examine the mechanism of specific hyporesponsiveness to major histocompatibility complex (MHC) class I-mismatched skin allografts induced by retrovirus-mediated gene transfer of an allogeneic class I gene into syngeneic bone marrow (BM). Using appropriate congenic recombinant mouse strains, we have mapped MHC determinants that are capable of restoring rapid rejection of K^b-bearing skin grafts. Our results indicate that either a single class I or a single class II alloantigen expressed on skin in association with K^b is able to restore the rapid rejection of K^b -mismatched skin grafts. These data suggest that third-party alloantigens expressed on skin in association with K^b abrogate hyporesponsiveness by providing T cell help. Consistent with this interpretation, spleen cells from mice reconstituted with K^b-transduced BM were unable to elicit a significant anti-K^b cytotoxic T lymphocyte response in vitro unless interleukin-2 was added to the culture medium. Skin graft survival was also analyzed on B10.AKM mice thymectomized 3–4 weeks post-reconstitution with K^b-transduced BM. Thymectomy did not result in significantly prolonged survival of B10.MBR skin grafts compared to euthymic controls, suggesting that even early after reconstitution, intrathymic deletion of K^b-reactive T cells must have been incomplete. Taken together, these data suggest that prolongation of skin allograft survival in this model is controlled at the level of T cell help.     

Cytotoxic T cell response against lymphoblasts infected with Moloney (Abelson) murine leukemia virus. Methodological aspects and H-2 requirements

A method for infection of lymphocytes with Moloney(Abelson) murine leukemia virus [M(A)-MuLV] is described. Only lymphoblasts obtained after stimulation of normal spleen cells by the B cell mitogen lipopolysaccharide (LPS) were satisfactory targets for virus-specific, secondary cytotoxic T lymphocytes (CTL), whereas spleen cells stimulated by the T cell mitogen concanavalin A were not. The secondary CTL response against M(A)-MuLV could be efficiently measured using M(A)-MulV-infected LPS blasts as stimulating cells for secondary in vitro restimulation and as target cells for virus-specific destruction. Cold target inhibition demonstrated virus specificity of CTL. The T cell character of the cytotoxic cells was demonstrated by their sensitivity to anti-Thy-1.2 treatment. Using syngeneic virus-infected LPS blasts as target and stimulator, CTL responses were measured with effector cells from C57BL mice of the H-2^b haplotype and of recombinant haplotypes sharing either K or D alleles with H-2^b. In analogy with previous studies on Moloney virus-specific CTL. it was observed that C57BL/6 (H-2^b) effector cells predominantly lysed D^b-compatible, virus-infected target cells; B10.A(5R), (K^bD^d) effector cells showed a poor CTL response against syngeneic, virus-infected target cells. The combined findings indicate the existence of an Ir gene in the H-2D region regulating the CTL response against Moloney leukemia virus.     

Peptides derived from the whole sequence of BCR-ABL bind to several class I molecules allowing specific induction of human cytotoxic T lymphocytes

Chronic myeloid leukemia (CML) is characterized cytogenetically by a t(9;22) translocation which generates a hybrid bcr-abl gene, encoding a p210^bcr-abl fusion protein. The induction in vitro of leukemia-specific T cells reactive with p210^bcr-abl is a strategy developed for an immunological therapeutic approach in CML. Peptides from the junction region of this chimeric protein have been considered as potential targets for a cytotoxic response against leukemic cells. However, only a few peptides encompassing the two p210^bcr-abl breakpoints have been shown to bind to the most common HLA class I molecules, which limits the number of patients who could benefit from this approach. We assume that the presence of chimeric BCR-ABL protein in leukemic cells may affect processing and delivery of peptides, possibly giving rise to new epitopes at the cell surface. We selected 162 peptides from the whole sequence of this protein, including 14 peptides of the b2a2 and b3a2 junctions, which had an anchor motif for a common HLA class I molecule. We tested their ability to bind to eight HLA class I molecules (HLA-A1, -A2, -A3, -A11, -B7, -B8, -B27, -B44). We identified 48 peptides from outside the junction region, with intermediate or strong binding capacities to these HLA class I molecules contrasting with only six junction peptides with a moderate binding capacity to HLA-A3/A11, -B8, or -B44 molecules. Moreover, cytotoxic T lymphocyte lines specific for various peptides outside the junction were generated from peripheral blood mononuclear cells of HLA-A2 or -B7 healthy donors and from one CML patient. These results contribute to evaluation of immunity to the BCR-ABL chimeric protein. Further studies are required to investigate whether such epitopes are correctly processed and presented by leukemic cells.     

Association Between H-2 Antigens and Thyroglobulin Influences the Immunogenicity of Thyroglobulin in Mice

To ascertain the role of H-2 in the immunogenicity of thyroglobulin, congenic strains of mice, B10.BR (H-2^khigh-responder) and B10.02 (H-2^d, low-responder) were immunized with purified thyroglobulin (from B10.BR and B10.D2) which was or was not passed through affinity columns of Sepharose coupled to anti-H-2^k or anti-H-2^d sera. Thyroglobulin absorbed with the same anti-H-2 as its source did not induce thyroglobulin antibodies or thyroid infiltrates in mice of the same strain and induced thyroid lesions but no antibodies in mice of the opposite strain. These experiments suggest that thyroglobulin, an autoantigen, is associated with syngeneic histocompatibility antigens in vivo and this association is important for the (auto) antigenicity of thyroglobulin.