Dissociation ofH-2 recognition by antibody and cytotoxic T cells of a cloned murine leukemia cell line

The differential expression of H-2 specificities recognized by antibody and by cytotoxic T lymphocytes (CTL) has been studied using a clone (FY7) of the C57BL/6 leukemia cell line FBL-3 (H-2 ^b /H-2 ^b ). Unlike C57BL/10 spleen cells, EL-4 lymphoma cells and Y57-2C leukemia cells (allH-2 ^b /H-2 ^b ), FY7 failed to induce the primary in vitro generation of anti-H-2^b CTL by (B10.A x A)F₁ (H-2 ^a /H-2 ^a or (B10.D2 x BALB/c)F₁ (H-2 ^d /H-2 ^d ) responder spleen cells. In addition, FY7 was not lysed by, and did not competitively inhibit anti-H-2^b CTL. Quantitative absorption tests with H-2K^b and H-2D^b antisera revealed that FY7 expressed these antigens in quantitatively similar amounts to EL-4. The H-2K^b product of FY7 appeared to be identical with that of C57BL/10 spleen cells both in apparent molecular weight and isoelectric point. Yet FY7 failed to inhibit anti-H-2K^b CTL competitively in a cold target inhibition assay. Possible mechanisms are discussed for the lack of T-lymphocyte recognition of the H-2K^b-gene product expressed by FY7.Abbreviations used in this paper CTL cytotoxic T lymphocytes - MHC major histocompatibility complex - MLC mixed lymphocyte culture - PAGE polyacrylamide gel electrophoresis     

A novel MHC class I-related molecule expressed on mouse thymic stroma cells and mature lymphocytes

A monoclonal antibody (mAb) TP-3 has been established by immunizing rats with the BALB/c mouse thymic epithelial cell line TEL-2. The TP-3 antigen is expressed on stroma cells of thymus, spleen, and lymph node in syngeneic BALB/c mice (H-2 ^d ). This antigen is also expressed at a low level on the cell surface of immature thymocytes, and at a high level on mature T and B cells. In allogeneic mice such as C57BL/6 (H-2 ^b ) or C3H (H-2 ^k ), no cells expressed the TP-3 antigen. Using H-2 congenic mice, reactivity with mAb TP-3 was found to map to a region of H-2D ^d L ^d or between D ^d and Qa, suggesting that TP-3 is a major histocompatibility complex (MHC) class I antigen. However, immunoprecipitation analysis indicated that this antigen is not identical to the classical mouse class I molecules in terms of molecular size, antigenicity, and tissue distribution.     

DonorIgh-linked genetic control of allotype-specific antibody response

Immunogenicity of allogeneic immunoglobulins in mice were studied, measuring the allotype-specific antibody activity by agglutination of allogeneic antibody-coated red blood cells. It was found that the serum from C.B-20 mice (Igh ^b , BALB/c-congenic) was uniquely immunogenic in BALB/c mice for allotype antibody response. Whereas the C57BL/6 (Igh ^b ) serum was immunogenic only when heat aggregated and/or combined with adjuvant, the ultracentrifugation-deaggregated C.B-20 serum was definitely immunogenic when administered in a moderate dose (100 μl/mouse). Even more surprising was the fast that very low doses (0.01–0.1 μl) of soluble C.B-20 serum, but not C57BL/6 serum, down regulated the allotype-specific response effectively. Genetic analysis on congenic mice suggested that the immunogenicity is controlled by donorIgh orIgh-V(Id-C.B) inasmuch as the serum from BALB/c-congenic C.B-20 (Igh-V ^b C ^b ), but not BALB/c-congenic BAB/14 (Igh-V ^a C ^b ), mice was active in BALB/c mice in soluble form. Further studies showed that the Id-C.B was dominantly expressed on the immunoglobulins of (BALB/c×C.B-20)F₁ and (C56BL/6×C.B-20)F₁ strains, and was originally derived from the C57BL/Ka strain. The major determinant for the antibody production was encoded inIgh-C, but not inIgh-V. It is suggested thatId-C.B controls the allotype-specific antibody response in an unusual manner, possibly acting as a unique determinant activating helper T cells.     

Analysis of cytotoxic mechanisms induced by minor histocompatibility antigens in the mouse.

Following immunization of BALB/c (H-2^d) mice against the P815Y (H-2^d) mastocytoma, two populations of effector cells could be identified in the spleen, namely, the cytolytic T cell and a cytostatic effector, which was resistant to anti-T-cell serum and complement and appeared to be adherent. Quantitative comparison of the activities of both effectors has been made with the levels of activity obtained following immunization across the major H-2 barrier in C57BL10 (H-2^b) mice. While T-cell activity was significantly lower in BALB/c mice, the non-T-cytostatic activity was greater compared with C57BL mice. Therefore, H-2 antigens do not appear to be essential for the efficient induction of the cytostatic effector.     

B-Cell responses to male-specific antigen(s) in mice

It has been found that B-cell responses to male-specific antigen(s) can be clearly demonstrated by reversed plaque assays. Female mice injected with syngeneic male spleen cells showed significant increases (greater than 100 × in some strains) in the number of immunoglobulin-secreting cells in lymph nodes draining the injection site. There was a variation in B-cell responsiveness between strains and this correlated only partially with previously reported T-cell responsiveness to the H-Y antigen. C57BL (H-2 ^b ) mice were among the most responsive, while CBA (H-2 ^k ), (CBA × C57BL)F₁, and BALB/c (H-2 ^d ) were all much less responsive. These results apparently open up a new approach to the investigation of B-cell responses to male-specific antigen(s).     

Homopoietic histocompatibility (Hh-1) phenotype and the regulation of its expression

Hybrid resistance (HR) is primarily controlled by the genes of the Hemopoietic histocompatibility-1 (Hh-1) locus within the H-2 complex. HR is a consequence of the Hh-1-controlled target determinants in homozygous parental strain mice and their absence in heterozygous F₁ hybrid mice. To examine the mechanism that controls the Hh-1 phenotype, three independent clones of somatic cell hybrids between parental lines EL-4 (C57BL/6 origin, H-2 ^b ) and R1 (C58 origin, H-2 ^k ) were studied. The line EL-4 is Hh-1^b-positive and is subject to HR by H-2 ^b heterozygous F₁ mice, but R1 lacks the Hh-1 ^b allele and is not susceptible to HR. Of the three hybrid clones, F263.2 is Hh-1^b-positive, whereas the other two, F262.2 and F264.2, are Hh-1-negative, as judged by these cells' capacity to compete in vivo with the grafted parental C57BL/6 bone marrow cells in the resistant (C57BL/6 × C3H)F₁ mice. All three clones express the H-2^b and H-2^k class I antigens equally well, are susceptible to activated NK cells to the same extent, and all carry four copies of chromosome 17. However, Southern analysis reveals that clone F263.2 contains three copies of H-2 ^b chromosome and one H-2 ^k , whereas the other two clones carry two copies each of the parental chromosome 17. The results suggest that the relative copy number of specific alleles is the crucial determinanr of the Hh-1 phenotype, and render unlikely both the gene dosage hypothesis and the trans-acting dominant suppression hypothesis to account for the noncodominant expression of the Hh-1 phenotype.     

Immune response to the H-X antigen on P815-X2

In a preceding report, the detection of an H-2-linked immune response to the H-X ^d antigen on the P815-X2 mastocytoma was demonstrated by the significantly increased survival of (C57BL/6 × DBA/2)F₁ (B6D2F1) male hybrids (H-X ^b ) compared with female siblings (H-X ^{b/H-X d} ) after injection with the histocompatible tumor (H-X ^d ). This interpretation was supported by the absence of this sex effect in reciprocal D2B6F1 hybrids (H-X ^d and H-X ^{d/H-X b} ). Additional findings presented in this paper support the conclusion that this sex effect is due to a true immunological response to H-X ^d : (a) Reciprocal (DBA/2 × C57BL/6 H-2 mutant)F₁ hybrids, as well as D2B6F1, failed to exhibit the sex effect: (b) the demonstration of the sex effect in (BALB/c × DBA/2)F₁ and (BALB/c-H-2 ^dm2 × DBA/2)F₁ hybrids and in (C57BL/10 × DBA/2)F₁ hybrids was consistent with the known H-X incompatibilities between the strains BALB/c and DBA/2 and C57BL/10 and DBA/2, respectively, previously demonstrated by skin grafting; and (c) the sex effect was not abrogated by castration of male B6D2F1 hybrids. Variability in the presence or absence of the sex effect was observed in various [recombinant inbred (RI) × DBA/2]F₁ hybrids and may be attributed to the influence of a regulatory non-H-2 gene which is closely linked to the gene coding for mouse kidney-androgen-regulated protein (KAP) but androgen-independent, or to variability in inheritance of the H-X ^b allele among the RI lines. It is proposed that the P815-X2 model may be utilized to type RI lines derived from a cross between C57BL/6 and DBA/2 for their H-X genotypes.Abbreviations B C57BL/6 origin allele - B6 C57BL/6 - B10 C57BL/10 - B6D2F1 (C57BL/6 × DBA/2)F₁ - B6 ^m D2F1 (C57BL/6 H-2 mutant × DBA/2)F₁ - bm10 B6.C-H-2 ^bm10 - C BALB/c - D DBA/2 origin allele - D2 DBA/2 - dm2 BALB/c-H-2 ^dm2 - H-X X chromosome-determined histocompatibility antigen of the mouse - Ir gene, immune response gene - KAP kidney androgenregulated protein - MST median survival time - RI recombinant inbred - SDP strain distribution pattern     

Time course study of H-2 and other antigen expression by hybrids of a myeloma cell line with inflammatory macrophages

The hybrids (the CANS lines) between inflammatory macrophages from C57BL/6N (B6) mice (H-2^b) and BALB/c mouse (H-2^d)-derived myeloma cell line NS1 in the early period after cell fusion showed no macrophage functions. However, most of the hybrids expressed these functions after prolonged cultivation accompanied with chromosome loss. In contrast, the hybrids initially displaying myeloma functions ( light chain production) lost this function when they exhibited macrophage functions. We studied the expression of cell-surface antigens in these hybrids and found that hybrids in the early period after cell fusion codominantly expressed both parental cell H-2 antigens (H-2K^b, H-2K^d, and H-2D^d) but not the H-2D^b antigen. On the other hand, aged hybrids strongly expressed the H-2 d antigen but lacked the H-2K^b antigen. Alternatively, these aged hybrids with macrophage functions expressed antigen(s) as detected with antiaged CANS-196 cell sera and asialo GM1 antigen, both of which were thought to be found exclusively on macrophages. Thus, the expression of cell-surface antigens in these hybrids was greatly altered after cell fusion.     

Receptor specificity,functional characteristics,and cell-surface phenotype of a highly selected anti-I-Ab-specific,long-term T-cell line

A highly selected alloreactive T-cell line was developed by repeated restimulation of B10.D2/n lymph-node cells with irradiated C57BL/10Sn (BIO) spleen cells in long-term MLC for up to 2 1/2 years. Continuous growth of the line requires restimulation every 2 to 4 weeks with fresh H-2^b stimulator cells. The line proliferates strongly against H-2^b but not againstH-2 ^d ,H-2 ^f ,H-2 ^q ,H-2 ^r , orH-2 ^s stimulators. Analysis of recombinant mouse strains showed that the proliferative response is directed against I-A^b but not K^b or D^b determinants. During the growth period of the line, strong cross-reactivity with H-2^p (B10.P) and weak cross-reactivity with H-2^k strains (e.g., CBA/J and B10.BR) was observed. A clone with exquisite specificity for I-A^b, but with no cross-reactivity with H-2^p or H-2^k was isolated from the line; thus clonal heterogeneity of the line still exists despite the highly selective growth conditions. — The majority of T cells from the line or clone were shown to bind I-A^b but not K^b or D^b determinants either spontaneously during restimulation with fresh B10 stimulator cells or via membrane vesicles expressing I-A^b determinants. No killing activity by the line in either specific or nonspecific cytolytic T-cell assays was observed nor was the T 145 glycoprotein, characteristic of killer T cells, detected.Abbreviations used in this paper B6 C57BL/6J - B10 C57BL/10Sn - Con A Concanavalin A - CTL cytotoxic T lymphocyte - FCS fetal calf serum - FDA fluorescein diacetate - FITC fluorescein isothiocyanate - Ia I-region-associated antigens - LPS lipopolysaccharide fromE. coli - Lyt T-lymphocyte-defined antigen - MLC mixed leukocyte culture - NP-40 nonidet P-40 - PAGE pofyacrylamide gel electrophoresis - PHA phytohemagglutinin fromPhaseolus vulgaris - PM plasma membrane - SDS sodium dodecyl sulfate - TCGF T-cell growth factor(s) - TdR thymidine     

Tumour-induced altered gastrointestinal steady-states: absence of MHC restriction in the paraneoplastic gastrointestine

Abstract The growth of a number of experimental rodent tumours including the Lewis lung tumour (LLca) progressively compromises the integrity of the host's gastrointestine by inducing cytokinetic alterations in the small bowel resembling those generally defining the intestinal phase of a graft-versus-host reaction (GVHR). To determine whether the induction of this paraneoplastic gastrointestine (PGI) involves, similar to a GVHR, a disparity between the MHC of the donor (LLca tumour) and the recipient (host), PGI development was evaluated in various LLca tumour-bearing murine strains that were either ‘syngeneic’[C57BL/6 and BL/10 (H-2^b)], ‘semisyngeneic’[B6D2F₁ (H-2^bd) and B6C3F₁ (H-2^bk)] or ‘allogeneic’[C3H/HeJ (H-2^k) and DBA/2 (H-2^d)] to the H-2^b LLca tumour. The temporal appearance and magnitude of a PGI developing in either LLca-syngeneic or semi-syngeneic hosts, but not the allogeneic strains, suggested that the mechanism(s) involved in PGI development, like the GVHR, was restricted by the MHC. Subsequent studies using congenic strains [B10.A (H-2^k) and B10.D2/nSn (H-2^d)], however, demonstrated that the mechanism(s) responsible for the PGI was restricted by the non-MHC loci of the C57BL mouse. These observations were supported by the appearance of a LLca-induced PGI in various B10.A congenic strains carrying mutations at the I-A or I-E/I-J loci of the MHC. Not unlike the intestinal phase of a GVHR, development of the PGI required the participation of enhanced mucosal mast cells which were limited in the WCB6F₁ (S1/S1^d) but not the (+/+) murine strains. These observations are discussed in light of the postulated premature migration of immature thymocytes that accompany tumour growth and their ability to non-specifically enhance (or suppress) cell mediated immune reactions in the host.     

Murine responses to (Tyr-Glu-Ala-Gly)n: II. H-2 and non-H-2 gene effects

Mice of the H-2^b haplotype responded to the sequential polymer poly(Tyr-Glu-Ala-Gly) in the in vitro T-cell proliferative assay, irrespective of whether they were homozygous or heterozygous at the H-2^b locus. The antibody responses of the H-2^b congenic mice to this polymer were variable, with A.BY and BALB.B showing responses better than those of C57BL/6 and C57BL/10 strains. The antibody responses of the F₁ progeny of (responder × nonresponder) strains of mice to this polymer are generally lower than the responder parents. F₁ mice with C57BL/10 background were the poorest responders. Studies with F₂ mice and backcross progenies of selective breeding of high and low antibody responder (C57BL/6 × BALB/c) F₁ to high responder C57BL/6 mice indicated that both non-H-2 genes and H-2 gene dosage effects influenced the magnitude of the humoral antibody responses. Animals having low responder non-H-2 background and only half the dosage of the responder immune response genes has greatly diminished antibody responses.     

The biological effects of syngeneic and allogeneic cytokine-expressing prophylactic whole cell vaccines and the influence of irradiation in a murine melanoma model

Allogeneic whole tumour cell vaccines are inherently practical compared with autologous vaccines. Cell lines are derived from allogeneic tumour, grown in bulk and then administered as a vaccine to the patient, following irradiation, which not only prevents any replication but also enhances antigen presentation. Protection is believed to occur through the presentation of antigens shared between the syngeneic and allogeneic tumours. Although cytokine-transfected tumour whole cell vaccines have been used clinically, little data is available comparing the effects of immunomodulatory cytokine-transfection directly on the same cells when used as both an allogeneic and autologous vaccine. To address this, weakly immunogenic B16-F10 (H-2^b) murine melanoma was transfected to secrete either GM-CSF, IL-4 or IL-7. Prophylactic vaccination of both syngeneic C57/BL6 (H-2^b) (B6) and allogeneic C3H/Hej (H-2^k) (C3H) mice showed the effects of transfected cytokine varied between models. Both GM-CSF and IL-7 significantly (P<0.05) increased the levels of protection within syngeneic B6 mice, but had a diminished effect (P>0.05) within C3H allogeneic mice. Allogeneic B16-F10 cells and syngeneic K1735 cells generated CTL against K1735 suggesting cross-reactive immunity. Using cells labeled with fluorescent dye we demonstrate that irradiated vaccines, of either syngeneic or allogeneic origin, appear to generate potent immune responses and fragments of either vaccine remain at the injection site for up to 9 days. This study shows that protection can be enhanced in vivo by using transfected cytokine, but suggests that irradiated whole cell vaccines, of either tissue-type, are rapidly processed. This leads to the conclusion that the cytokine effects are transient and thus transfection with cytokine may be of limited long-term use in situ.     

Activation of specific suppressor cells with heat-treated allogeneic tumor cells

The ability of heat-treated allogeneic cells to induce suppressor cells was examined. The tumor cell lines EL-4 (H-2^b) and P815-X2 (H-2^d), were heated to 56 °C for 10 min and injected intravenously into mice of the DBA/2J (H-2^d) and C57BL/6J (H-2^b) strains, respectively. After 4 days, the splenocytes of the treated mice were mixed with normal spleen cells and cultured for 5 days with allogeneic tumor cells. The cytotoxic T-cell response was reduced in cultures of these cell mixtures. An allogeneic difference was required to induce suppression because the syngeneic combination did not induce suppressor cell activity. Furthermore, the induction of cytotoxic T cells to the C118 cell line (H-2^k) was not suppressed by this procedure, which suggests that the suppression was haplotype specific. These suppressor cells were sensitive to anti-Thy 1.2 and complement, cortisone, and cyclophosphamide, but insensitive to irradiation. These are characteristics similar to suppressor cells activated by intact cells. Heat treatment abrogated the tumor cell's ability to induce a proliferative and a primary, but not a secondary, cytotoxic T-cell response. The heat-treated cells also lost their ability to function as cold target inhibitor cells, but retained the same quantity of serologically detected antigens as the intact cells. These results suggest that the serologically detected antigens are responsible for the activation of the suppressor cells of the cytotoxic T-cell response.     

Genetic control of the target structures recognized in hybrid resistance

Hybrid resistance of lethally irradiated (C57BL/6 × DBA/2)F₁ and (C57BL/10 × C3H)F₁ hybrid mice to the engraftment of parental C57BL/6 or C57BL/10 bone marrow cells is controlled by the H-2-linked Hh-1 locus. This resistance can be specifically blocked or inhibited by the injection of irradiated spleen cells from lethally irradiated, marrow reconstituted donor mice of certain strains. By testing the ability of regenerating spleen cells from various donor strains to block the resistance, we studied the genetic requirements for the expression of putative cell-surface structures recognized in hybrid resistance to H-2^b marrow cells. Strains of mice bearing informative intra-H-2 or H-2/ Qa-Tla recombinant haplotypes provided evidence that the Hh-1 locus is located telomeric to the H-2S region complement loci and centromeric to the H-2D region class I locus in the H-2 ^b chromosome. Two mutations that affect the class I H-2D ^b gene have no effect on Hh-1 ^b gene expression. The H-2D region of the H-2 ^S haplotype contains an allele of the Hh-1 locus indistinguishable from that of the H-2D ^b region, as judged by the phenotypes of relevant strains and F₁ hybrids. Collectively these data indicate that the Hh-1 locus is distinct from the class I H-2D (L) locus in the H-2 ^b or H-2 ^s genome, and favor the view that the expression or recognition of the relevant determinants is not associated with class I gene products.Abbreviations used in this paper BM(C) bone marrow (cells) - CML cell-mediated lympholysis - CTL cytotoxic T lymphocytes - FBS fetal bovine serum - HBSS Hanks' balanced salt solution - SC spleen cells from irradiated, bone marrow-reconstituted mice Address correspondence to: Dr. I. Najamura, Department of Pathology, School of Medicine, State University of New York at Buffalo, Buffalo, NY 14214, USA     

A cross-over chromosome combiningIg heavy chain genes of two mouse strains

Two congenic strains of mice were bred in Konstanz that bear theIg heavy chain allotype gene of the C57BL/6 (Ig-1 ^b ) in a BALB/c background genome. One line (CB-8K) underwent eight backcross generations to BALB/c before sister-brother mating was initiated. For the other line (CB-16KN) backcrossing was continued for eight further generations, then a homozygousIg-1 ^b /Ig-1 ^b strain was produced by sister-brother mating. Both lines were tested for four V_H markers of the BALB/c and one of the C57BL parent. The CB-16KN strain expressed the C57BL marker V_HNP^b together with the C57BL allotype marker, and failed to express the three BALB/c markers, V_HDEX, V_HS117, V_HphOx and V_HNP^a. It thus resembled the CB-20 strain.Strain CB-8K expressed the V_HNP^b marker of C57BL but also all the four BALB/c markers that were tested. The strain appeared more heterogeneous than the CB-16KN strain, and a subline was bred from two exceptional mice that did not express the V_HNP^b marker. This subline (CB-8KN) expressed the BALB/c marker V_HNP^a regularly, and was negative for the V_HNP^b marker. It thus resembles the BAB-14 line.The crossing over event thus must have happened in one of the two meioses, which led to the CB-8K line. As BAB-14 is derived in an analogous manner to a branch of the backcross of Potter and Lieberman, which ended up in CB-20, the unexpected finding is discussed that two independent crossing over events (in CB-8KN and BAB 14) within theIg heavy chain gene region have taken place at approximately the same stage of two breeding programs.Recipient of an EMBO fellowship during part of the study.     

Failure to Reject an Allografted Tumor after Elimination of Macrophages in Mice

After an i.p. transplantation of an allogeneic tumor (Meth A) to C57BL/6 mice, a macrophage (MΦ)-rich, non-T, non-NK cell population is induced as the major infiltrate and cytotoxic cells. We here evaluated the role of the MΦs in the rejection of allografted Meth A cells and characterized the MΦs in comparison with other well-known MΦs. At all time intervals after transplantation, the highest cytotoxic activities against Meth A tumor were obtained with the MΦ-rich population. In addition, the lymphocyte-rich population had a significant but low cytotoxic activity, whereas two other population types, granulocytes and large granular cells, were inactive. When the MΦ-rich or the T cell-depleted MΦ-rich population was i.p. transplanted simultaneously with Meth A cells into untreated C57BL/6 mice, the tumor cells were rejected without growth. After specific elimination of MΦs by in vivo application of dichloromethylene diphosphonate-containing liposomes, the cytotoxic activity against Meth A cells was hardly induced at the transplantation site of Meth A cells and the allografted Meth A tumor continued to grow, indicating that a type of MΦ is the effector cell essential for the rejection. In contrast to other well-known MΦs, the cytotoxic activity against Meth A cells was cell-to-cell contact dependent and soluble factor (e.g., NO and TNF-α) independent. Moreover, the cytotoxic activity of the MΦs (H-2^b) against ⁵¹Cr-labeled Meth A (H-2^d) cells was inhibited by the addition of unlabeled H-2^d, but not H-2^a, H-2^k or H-2^b, lymphoblasts as well as Meth A cells, implying the specific interaction of the MΦs with H-2^d cells.     

H-2 class I antigen expression on mouse teratocarcinoma cell lines

Immunity against PCC3 teratocarcinoma cells (129, H-2 ^b) was induced in allogeneic (C3H, H-2 ^k) mice by preimmunization with L cells (C3H, H-2 ^k) expressing cosmid-introduced K ^b or D ^b genes, but not with nontransfected L cells. In addition, the growth of PCC3 cells in sublethally irradiated (C3H × B6-H-2 ^bm1)F₁ and (C3H × B6-H-2 ^bm13 )F₁ mice bearing the K ^bm1 and D ^bm13 mutations, respectively, was either prevented, stopped, or delayed in comparison with the (C3H × B6)F₁ (k × b) mice, which failed to reject the PCC3 cells. The teratocarcinoma line OC15S was exceptional because it reacted specifically with K^b- and D^b-specific (but not I^b-specific) alloantisera, and because K^b- and D^b-specific antibodies could be absorbed by OC15S cells. The subpopulation of OC15S cells bearing the ECMA-7 antigen characteristic for embryonic carcinoma (EC) cells was isolated by the fluorescence-activated cell sorter and was shown to react specifically with K^b- and D^b-specific antisera. These experiments show that teratocarcinoma cells express antigens similar or identical to the K-and D-region products of differentiated cells. The lack of expression of class I antigens is thus neither a condition nor a consequence of the pluripotentiality of the EC cells. The exact nature of the major histocompatibility complex antigens on EC cells has yet to be established using the methods of molecular biology and biochemistry.     

A genetic analysis of natural resistance to nonsyngeneic cells: The role of H-2

The genetic control of natural resistance in vivo to four natural killer (NK) cell-resistant H-2 homozygous lymphoid tumor cell lines was investigated by following the survival and organ distribution of cells prelabeled with radioactive iododeoxyuridine. Backcross mice derived from DBA/2J and CBA/J parents were injected with H-2 ^dtumor cells and tumor cell elimination was lowest in H-2 ^dhomozygotes. Natural killer cell activity was also reduced in mice with the H-2 ^dhaplotype, but no direct correlation between NK cell levels against YAC-1 or SL2-5 lymphoma cells and natural resistance in vivo was demonstrable. Analysis of 23 BXD recombinant inbred strains indicated that natural resistance to H-2 ^dtumors was restricted to H-2 ^bstrains. There was no direct association of NK cell activity with H-2 type in the BXD strains and NK cell levels did not correlate with tumor survival in vivo. By comparing natural resistance to H-2 ^dand H-2 ^btumors in DBA/2, C57BL/6, B6D2F₁, and B10.D2 mice we found that H-2 nonidentity between the tumor and the host, rather than the host H-2 haplotype, determined whether natural resistance occurred. Again, NK cell activity against YAC-1 cells was not predictive of tumor survival in these strains. These results provide genetic evidence that NK cells alone cannot account for natural resistance to H-2 nonidentical cells of hemopoietic origin.     

Selective reversal of H-2 linked genetic unresponsiveness to lysozymes

Genes outside of the mouse major histocompatibility complex (H-2) were found to be capable of specifically reversing the previously described nonresponsiveness to hen egg-white lysozyme (HEL) owing to H-2 ^b immune response (Ir) genes. C3H.SW, BALB.B, and C57L, all of the H-2 ^b haplotype, showed responsiveness to HEL, but not to human lysozyme (H UL). Mapping of the reversing gene(s) was attempted by testing H-2 ^b recombinant inbred (RI) strains of mice carrying C3H, BALB, and C57L non-H-2 ^b genes. Analysis of the strain distribution pattern of responsiveness with both CXB and BXH RI strains was consistent with the location of the responsible site within the H-3 region on chromosome 2. The anti-HEL proliferative responsiveness in two H-3 congenic strains of mice, B10.C(28NX) ^SN and B10.C-H-3 ^{cH-3 a} , that have BALB/c genes within the H-3 region confirmed the mapping, as well as localized the reversing gene(s) near the Ir-2 gene. The data are discussed with regard to the site of expression of the reversing gene(s) and its mechanism of action.Abbreviations used in this paper MHC major histocompatibility complex - HEL hen egg-white lysozyme - Ir immune response gene - HUL human lysozyme - SDP strain distribution pattern - PFC plaque-forming cells; ₂ m, ₂-microglobulin - CFA complete Freund's adjuvant - PT-LN parathymic lymph nodes - RI recombinant inbred mice     

Interacting genetic factors controlling the antibody response against the H-2.2 specificity

The antibody response against the H-2.2 specificity has been studied in three H-2 ^d strains, B10.D2, DBA/2, and BALB/c, and their hybrids (B10.D2 × DBA/2)F₁ and (B10.D2 × BALB/c)F₁. The genetic control of the response appears to be complex: The three pure strains are responders, whereas both hybrids when immunized with C3H-HTG are nonresponders. Individual analysis of N3 offspring is compatible with the idea that, in this combination, an Ea-4 incompatibility between donor and immunized strain is necessary for the anti-H-2.2 response to occur. H-2 ^d /H-2 ^k hybrids (B10.BR × B10.D2)F₁ or (B10.BR × DBA/2)F₁ are responders when immunized with C57BL/10 (H-2 ^b ) but not with B10.A(2R) (H-2 ^h ), indicating that simultaneously recognized H-2 specificities are necessary for the anti-H-2.2 response.