The spatial relationship of the viral and H-2 antigens recognized by anti-viral CTLs

With the use of monospecific rabbit anti-G protein and mouse monoclonal anti-H-2K^k, we have analyzed the spatial relationship of the serologically defined H-2K^k antigens and the major surface glycoprotein (G protein) of vesicular stomatitis virus (VSV) to those antigens recognized by B10.A (k, d) anti-VSV cytotoxic T lymphocytes (CTLs). The ability of monoclonal anti-H-2K^k or rabbit anti-G protein to inhibit specifically the cytolytic activity of B10.A anti-VSV CTLs indicates that the G protein and the H-2K^k molecules are in close proximity to the viral and H-2K^k antigens recognized by the anti-VSV (CTLs. By the method of sequential immunoprecipitation, we also demonstrated that only 10–30 percent of the serologically defined G and H-2K^k molecules are in theG-H-2K ^k complexes.Abbreviations used in this paper Con A Concanavalin A - cpm counts per minure - CTLs cytotoxic T lymphocytes - E: T ratio effector: target ratio - G major surface glycoprotein of VSV - MHC major histocompatibility complex - MOI multiplicity of infection - NP40 Nonidet-P40 - PAGE polyacrylamide gel electrophoresis - PBS phosphate-buffered saline - SaCI Staphylococcus aureus, Cowan I strain - SDS sodium dodecyl sulfate - UV ultraviolet light     

Immunological properties of Fc receptor on lymphocytes. 6. Characterization of suppressive B-cell factor (SBF) released from Fc receptor-bearing B cells.

EA, i.e., antigen-antibody complexes are able to induce an antigen-nonspecific suppressive factor(s) from FcR⁺ B cells by binding on FcR. This factor, termed “suppressive B-cell factor (SBF)” was only effective on H-2 compatible, but not on H-2 incompatible spleen cells in an adoptive cell transfer system. Furthermore, SBF, prepared from B10.A (H-2^a) splenic FcR⁺ B cells, suppressed the adoptive primary response of B10.D2 mice (H-2^d), in addition to A/J mice (H-2^a) against DNP-DE, by the pretreatment of cells with SBF in vitro. Absorption with affinity columns demonstrated that active components) of SBF from C3H/He mice (H-2^k) was eliminated by both B6 anti-CBA (H-2^b anti-H-2^k) and B10.D2 anti-B10.BR (H-2^d anti-H-2^k), but not B10 anti-B10.A (H-2^b anti-H-2^a). In contrast, the suppressive activity of SBF was eliminated neither by anti-mouse Ig nor by a heat-aggregated human γ-globulin column. These results indicate that SBF contains a product coded by the right-hand side of H-2 gene complex, but does not contain Ig determinants nor FcR. Thus, it is conceivable that a compatibility of the right-hand side of H-2 gene complex is required for inducing effective suppression of spleen cells by SBF. SBF was considered to be a trypsin-resistant and heat-labile substance with a molecular weight of 30,000–63,000. The target cells for SBF were FcR^? B precursors, but not helper T cells.     

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     

Complex genetic effect of B10.D2 (M504) (H-2dm1) mutation

Serological and capping experiments show that the strain B10.D2 (M504) carrying the mutant haplotypeH-2 ^dm1 has two molecules in the products of theD region: H-2D^dm1 and H-2L^dm1 which are detectable by anti-H-2.4 and by anti-H-2.28 sera, respectively. Both these molecules differ serologically from the H-2D^d and H-2L^d molecules of the original (nonmutant) strain B10.D2. A third molecule, different from H-2D and H-2L, was detected inH-2 ^d ,H-2 ^dm2 but not inH-2 ^dm1 products.     

Molecular heterogeneity of D-end products detected by anti-H-2.28 sera

In capping experiments with peripheral T lymphocytes, two anti-H-2.28 sera (AKR anti-AKR.L, anti-K^b, and C3H anti-0H.B10, k anti-b) that do not contain any Qa-2-specific antibodies are able to redistribute not only the H-2.28-positive H-2 molecules, but also Qa-2 molecules. This is due to the capacity of these sera to react with Qa-2 molecules because on cells where all known molecules of the H-2 ^d haplotype were capped (K1^d, K2^d, D^d, M^d, L^d, L2^d), both antisera still reacted when the cells came from a Qa-2 positive D^d strain (B10.A) but not when the cells were of Qa-2 negative strain (BALB/cByA). The reaction with la and non-H-2 antigens was excluded in these experiments. These data show that Qa-2 and H-2 antigens share some specificities of the H-2.28 family. Other anti-private and anti-public anti-H-2 sera failed to react with the Qa-2 molecules.     

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.     

Fine specificity of a proliferating T-cell clone activated by a conformational determinant of the I-Ek molecule

We have examined the fine specificity of a stable Thy-1.2⁺, Lyt-1.2⁺, Lyt-2^–, and I-A^s– anti-I-E^k proliferating T-cell clone isolated from an A.TH anti-A.TL secondary mixed lymphocyte culture. Spleen cells from various I-A^k, E^k strains induced either a strong (A.TL, OH, and CBA) or a weak (AKR and B10.BR) proliferative response, although such cells expressed at their surface similar amounts of I-E^k antigens. Analysis of H-2 recombinant strains indicated that this clone recognized a conformational determinant carried by the E ^k E ^k dimer, but not on the Ea chain per se. Among the Fl hybrid strains in which the combinatorial E ^k E ^k product was detected by cellular binding with monoclonal E ^k -specific antibodies (mAb), some [(BIO.S(8R) × BlO.HTT) but not others (for example, B10.A(4R) × B10.A(5R)] were stimulatory. Seventeen anti-E^k mAb, regardless of the three spatially separated domains that they defined by antibody binding competition, completely inhibited the restimulation of this clone, whereas 15 other anti-A^k mAb failed to do so. This clone was not reactivated by stimulating cells from strains with the H-2 haplotypes p, j, v, b, r, and s but it proliferated strongly against cells from several H-2 ^d or H-2 ^q strains. Genetic evidence or blocking studies with selected mAb assigned these cross-reactive mixed lymphocyte reaction determinants to the A^d or A^q molecules, respectively. The data support the conclusion that alloreactive T cells may define a polymorphism of I-region coded products not detected by serological analyses and extend at the T-cell level the observations of serological cross-reactions between A and E molecules.     

Effect of anH-2 mutation on cytotoxic T cell recognition. Specific antigen can determine the pattern ofH-2 restriction

Hz1 (H-2 ^bm1 ) mice, an H-2 mutant strain derived from C57BL/6(H-2 ^b ), were either injected with vaccinia virus or had their spleen cells sensitized in vitro with syngeneic TNP-modified cells. The cytotoxic cells generated were tested for their activity against target cells that were either infected with vaccinia virus, TNP-modified, or both vaccinia infected and TNP-modified.Hz1 anti-TNP cytotoxic cells specifically lysed syngeneic target cells that were trinitrophenylated but not infected with vaccinia virus, while anti-vaccinia cells specifically lysed vaccinia infected target cells but not TNP-cells. Hz1 (H-2K ^bm1 D ^b ) anti-TNP effector cells killed B10.A(5R)-TNP (H-2K ^b D ^d ) targets, indicating that there is cross-reactivity between TNP-H-2K^b and TNP-H-2K^bm1. On the other hand, there is no cross-reactivity between vaccinia-H-2K^b and H-2K^bm1, since Hz1 anti-vaccinia effector cells did not kill vaccinia infected B10.A(5R) targets.Since Hz1 anti-TNP effector cells lysed B10.A(5R) target cells that were first infected with vaccinia virus and then derivatized with TNP, virus does not mask cross-reactive determinants shared by TNP-H-2K^b and H-2K^bm1. Additional experiments showed that Hz1 anti-TNP effector cells lysed TNP-modified and vaccinia infected B10.A(5R) target cells irrespective of the virus concentration used for infection or the time of addition of virus. Further, there are no detectable quantitative differences between C57BL/6 and Hz1 anti-TNP effector cells in their ability to kill TNP-5R targets.The cytotoxic effect of Hz1 anti-TNP effector cells on B10.A(5R)-TNP targets could not be blocked with TNP derivatized inhibitor cells that carry theH-2D ^d region allele. Thus, the ability of anti-TNP H-2K^b effector cells to cross-react with H-2K^bm1 cannot be explained by a cross-reaction between H-2K^bm1 and H-2D^d.Abbreviations used in this paper TNP trinitrophenol - PFU plaque forming unit - Con A Concanavalin A - BSS balanced-salt-solution - FCS fetal calf serum - TNBS trinitrobenzene sulfonic acid - PBS phosphate-buffered-saline     

Use ofH-2 mutations to quantitate alloreactivity: Alloreactivity is strongest against H-2 antigens which are closest to self

Lymph-node cells fromH-2 allogeneic, intra-H-2 recombinant andH-2 mutant congenic strains were sensitized in limiting dilution cultures to quantitate the cytotoxic T-lymphocyte precursor frequencies (CTL.Pf) against antigens encoded by different regions of theH-2 complex. When fourH-2K ^b mutants of C57BL/6 (B6) were tested, we observed anti-B6 CTL.Pf that were as high or higher than those of recombinant strains which differ from B6 at theK end of theH-2 complex. Relative to strains completelyH–2 allogeneic to B6, the CTL.Pf inH-2 ^bm1,H-2 ^bm3 andH-2 ^bm5 averaged 40–50 percent, andH-2 ^bm8 averaged 140 percent. Recombinant strains B10.A (4R) and B10.D2 (R103), which differ from B6 at theK end of theH-2 complex, averaged 60 percent of the completelyH-2 allogeneic value. Since the mutant and wild-type gene products have no serological and minimal structural differences relative to other alleles atH-2K, these results indicate that the CTL.Pf does not increase with increasing H-2 antigenic disparity between any two strains. Rather, the data suggests that the T-cell receptor repertoire recognizes those H-2 molecules or determinants closest to self.     

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     

H-41, a new minor histocompatibility locus. I. Histogenetic analysis

The B10.STA12 mouse congenic line inherited from the wild mouse parent not only the H-2w13 haplotype but also an allele at a minor H locus, which we designate H-41. This allele (H-41a) differentiates the B10.STA12 line from B10.STA10 and B10.LIB55, which carry identical H-2w13 haplotypes but a different H-41 allele (the H-41b, also present in the background strain C57BL/10Sn). The B10.STA12 and B10.STA10 lines reject each other's skin grafts and generate cytolytic T lymphocytes (CTL) after in vivo immunization and in vitro restimulation with cells of the partner strain. The B10.STA12 anti-B10.STA10 CTL react with B10.STA10, B10.LIB55, and B10.STA39 target cells and with cells of F1 hybrids between the responder strain B10.STA12 and strains C57BL/6, C57BL/10, C57L, BALB/c, A, AKR, WB, DBA/1, and DBA/2 but fail to react with (C3H x B10.STA12) F1 and (CBA x B10.STA12) F1 cells. The B10.STA10 anti-B10.STA12 CTL react with B10.STA12, B10.P, and C3H.NB cells but fail to react to (B6 x B10.STA10) F1 target cells. The CTL reactivity in both combinations is Dp restricted. The B10.STA10 anti-B10.STA12 CTL exhibit, in addition, a cross-reactivity with B10.SAA48 cells that may be directed at one of the alloantigens controlled by the H-2 haplotype of this strain.     

Immunogenetic analysis ofH-2 mutations

A.BY, B10.LPa, and B10.129(5M) mice were presensitized in vivo against B10.A(5R) cells and then restimulated in vitro by the same cells in the standard CML assay. The effector cells thus generated lysed not only B10.A(5R), but also C57BL/6 targets, indicating that, in addition to anti-H-2D_d response [measured on the B10.A(5R) targets], response to minor histocompatibility (H) antigens (measured on the C57BL/6 targets) also occurred. The latter response was directed against multiple minor H antigens in the case of the A.BY effectors, and against H-1 and H-3 antigens in the case of B10.129(5M) and B10.LPa effectors, respectively. The sensitization against minor H antigens occurred in the context of H-2K^b H-2D^d antigens, but by testing the response on C57BL/6 targets, only cells reacting with minor H antigens in the context of H-2K^b were assayed. The same effector cells were then tested against H-2^b mutant strains, in which theH-2K ^b allele was replaced by a mutant one. All three effector types [A.BY, B10.LPa, and B10.129(5M)] behaved in a similar way: they all reacted with theH-2 ^bg1 mutant to the same degree as withH-2 ^b, they did not react at all or reacted only weakly with theH-2 ^bd andH-2 ^bh mutants, and they reacted moderately or strongly with theH-2 ^ba mutant. The degree of crossreactivity with the mutants reflects, with one exception, the degree of relatedness of these mutants toH-2 ^b, as established by other methods. The one exception is theH-2 ^ba mutant, which is the most unrelated toH-2 ^b, and yet it crossreacted strongly. Further testing, however, suggested that in this instance the crossreactivity was probably directed against H-2 antigens: the anti-H-2D^d effectors apparently crossreacted with the H-2K^ba antigens. This finding is an example of cell-mediated crossreactivity between the products of two differentH-2 genes (H-2K andH-2D). It is also an example of anH-2 mutation generating an antigenic determinant known to be present in another strain.     

Murine antigen H-2.7: Its genetics,tissue expression,and strain distribution

Reinvestigation of alloantisera containing antibodies to murine antigen H-2.7 revealed that the crucial recombinant, A.TFR1 (H-2 ^an1 ), which was reported to separate theH-2G locus from theSs-Slp loci, has ak-like instead off-like H-2.7 antigen. Therefore, the crossover position inH-2 ^an1 and the position of the G locus in theH-2 map are now uncertain. By using the hemagglutination-serum inhibition test, anti-H-2.7 reactive substance was found to be present in normal mouse serum in a strain-specific manner. Tissue distribution study by absorption analysis indicated that H-2.7 antigen is present, in addition to RBCs, on spleen and lymph node cells, but is absent on thymus cells. Thirty B10.W congenic lines were analysed for the presence of the H-2.7 antigen. Two lines (B 10.CHA2 and B 10.KPA44) were found to be H-2.7 positive by both direct hemagglutination and absorption tests.Abbreviations used in this paper ACT Ammonium chloride Tris-buffer - BSA Bovine serum albumin - HA Hemagglutination - HASI Hemagglutination serum inhibition - HBSS Hanks balanced salt solution - PBS Phosphate buffered saline - PVP Polyvinylpyrrolidone - RBCs Red blood cells     

Role of mouse and human class II transgenes in susceptibility to and protection against mouse autoimmune nhyroiditis

 Mouse experimental autoimmune thyroiditis (EAT), a model for Hashimoto’s thyroiditis, is induced by immunizing with mouse thyroglobulin (MTg). To study the extent of H2A involvement in EAT, we introduced AaAb genes from susceptible k mice into resistant or intermediately susceptible strains which do not express H2E molecules. Thyroiditis was severe in resistant B10.M (H2 ^f ) mice carrying the double transgene Aa ^k Ab ^k . Likewise, thyroid infiltration was significantly extended in intermediate B10.Q (H2 ^q ) mice with the same transgene. To examine the effect of H2E molecules in the presence of H2A-mediated susceptibility, we introduced an Ea ^k transgene into E^– B10.S mice to express the Eβ^s molecule and observed significant reduction in EAT severity in B10.S(E⁺) mice. On the other hand, the presence of an Eb ^d transgene in B10.RQB3 (H2A ^q ) mice resulting in the expression of H2Eβ^d molecules did not alter EAT susceptibility, suggesting a role for Eb gene polymorphism in protection against EAT. We have shown recently that the HLA-DRB1 ^* 0301 (DR3) transgene conferred EAT susceptibility to B10.M as well as class II-negative B10.Ab⁰ mice. However, we report here that the HLA-DQB1 ^* 0601 (DQ6b) transgene in B10.M or HLA-DQA1 ^* 0301/DQB1 ^* 0302 (DQ8) transgene in class II-negative Ab⁰ mice did not. These studies show the differential effects of class II molecules on EAT induction. Susceptibility can be determined when class II molecules from a single locus, H2A or HLA-DQ, are examined in transgenic mice, but the overall effect may depend upon the presence of both class II molecules H2A and H2E in mice and HLA-DQ and HLA-DR in humans. Received: 28 January 1997 / 24 March 1997     

H-2-associated specificity of virus-immune cytotoxic T cells fromH-2 mutant and wild-type mice: M523 (H-2K ka ) and M505(H-2K bd ) do,M504 (H-2D da ) and M506(H-2K fa ) do not crossreact with wild-typeH-2K orH-2D

B10.A(3R) (H-2K ^b ) mice infected with lymphocytic choriomeningitis virus (LCMV) or vaccinia virus generate cytotoxic T cells capable of specifically lysing virus-infected macrophage target cells fromH-2K ^b mutant mice M505 (H-2K ^bd ), and vice versa. Similarly, virus-immune B10.A(4R) (H-2K ^k ) T cells specifically lyse infected targets from M523 (H-2K ^ka ), and vice versa. In contrast, virus-specific cytotoxic T cells from neither M504 (H-2D ^da ) and B10.A(5R) (H-2D ^d ) nor M506 (H-2K ^fa ) and B10.M(11R) (H-2K ^f ) mutually crossreact at the cytotoxic effector-cell level. As far as tested, the crossreactivity patterns between wild-type and mutantK orD specificities are identical for LCMV- and vaccinia virus-immune spleen cells. Although this finding is no proof for either the altered self nor the dual recognition concept of T-cell recognition, it may be compatible with the latter model.     

Serological cross-reactivity between products of separate I regions

A B10.S(7R) anti-B10.S(9R) serum (anti-IJE ^k C ^d ) contained, as expected, antibodies specific for the I-E-subregion-encoded determinant Ia.7. However, tests on recombinant haplotypes demonstrated a series of unexpected weak extrareactions which could be interpreted to be directed against antigenic determinants encoded in the I-A subregion of the H-2 complex. The same type of extrareaction was observed in eluates from I-A ^s , I-E ^k cells coated with A.TH anti-A.TL (I-A ^s , I-E ^s anti-I-A ^k , I-E ^k ) serum. This reactivity in serum and eluates could be interpreted as cross-reactivity between products of the I-E and I-A subregions.     

MHC epitopes of Ks and Dd restrict the same population of cytolytic T lymphocytes

When A. SW (H-2 ^s) mice are immunized with B10.S (H-2 ^S) epidermal cells, cytolytic T lymphocytes are evoked that efficiently lyse B10.D2 (H-2 ^d) as well as B10.S target cells. Immunogenetic analysis of this apparent H-2-unrestricted killing revealed that the most plausible explanation was a sharing of an H-2-restricting epitope by H-2K^S and H-2D^d molecules.     

Polymorphic and autoreactive H-2-specific monoclonal antibody isolated after injections of syngeneic sendai virus-coated lymphocytes

An H-2-specific monoclonal antibody (mAb Q-1) was obtained from B10.Q (H-2 ^q) mice injected with syngeneic Sendai virus-coated cells. The IgM monoclonal antibody recognizes the public determinant H-2.25 shared by H-2 ^k (K ^k) and H-2 ^r haplotypes and cross-reacts with H-2^d, H-2^s, H-2^p, and H-2^q cells, the latter being the haplotype of the challenged B-cell donor. The binding of mAb Q-1 to H-2^d, H-2^s, H-2^q, and H-2^p cells was lower than to H-2^k and H-2^r and of decreasing affinity but could be clearly distinguished from the negative reactions with H-2^b and H-2^f cells. MAb Q-1 distinguishes between Sendai virus-coated and uncoated lymphocytes only cells with low-affinity binding. On virus-coated or infected (H-2^p, H-2^q, H-2^d, H-2^s) cells lysis was stronger than on normal lymphocytes. We interpret the enhanced lysis of Sendai virus-positive cells by mAb Q-1 to be due to recognition of a modified exposure of public H-2 determinants induced by Sendai virus.On leave from The Institute of Immunology and Experimental Therapy, Wroclaw, Poland     

Dominant reduced responsiveness controlled by H-2(Kb)Ab. a new pattern evoked by Thy-1 antigen and F liver antigen

In the most frequently used panel of H-2 recombinant strains, B10.A, B10.A(4R), B10.A(5R), and B10, inhibition of the immune response has hitherto mapped to H-2E. Inhibition of the responses to Thy-1 antigen and to F liver protein, as described here, maps in a novel pattern to H–2K ^b A ^b , and presumably to H–2A ^b .Enhancement of the adoptively transferred anti-Thy-1 response by treatment with CD8-specific antibody suggests, very provisionally, that T cells with suppressive activity mediate the inhibition. The evolution of this new pattern, and of dominant reduced responsiveness in general, is discussed and its relevance to immunological diseases assessed. An enzyme-linked immunosorbent assay (ELISA) for F-specific antibodies is introduced.     

A histocompatibility region (H-2IC) in theIC region of theH-2 complex of the mouse

Skin graft rejection in congenic pairs of mice differing only at theH-2 complex appears to be influenced by at least 3 genes (H-2K, H-2D, H-2I); we now describe a fourth,H- 2IC: Grafts transplanted across anIC difference are sometimes rejected. TheI-C regions of three differentH-2 haplotypes (d,k,s) were studied in different combinations, and variable patterns emerged: (a)IC ^d : B10.S(7R) show delayed or no rejection of first B10.S(9R) grafts, but grafts to immunized recipients were usually rejected in 20 days; (b)IC ^k : in two combinations (A.AL A and B10.HTT B10.S[9R]) first grafts were rejected by day 30, although grafts to immunized mice showed a different pattern. In the third combination (B10.HTTB10.S[7R]) first grafts were retained but immunized mice rejected their grafts, (c)IC ^s : B10.S(9R) regularly reject B10.S(7R) first grafts, but immunized mice retain their grafts. In two other combinations first grafts were retained but grafts to immunized recipients were rejected; while in a third combination rejection did not occur at all. The background of the recipient appeared to be important in determining the variable pattern of rejection, and there is evidence for a similarity of the H-genes inIC ^s andIC ^k , and inIC ^k andIC ^p . Graft rejection occurred independently of known differences in Ia specificities, indicating thatH-2IC and the genes determining Ia specificities are probably different, although when grafts were performed in the presence of known la differences, graft rejection usually occurred.