Intra-H-2 recombination in the mouse

Serological characterization of threeK-S interval recombinant strains, TBR2 (H-2 ^at2 ), TBR3 (H-2 ^at3 ) and AIR1 (H-2 ^a2 ) was performed using anti-H-2, Ia, Ss and Slp antisera. The data presented here reveal that the crossover events in both TBR2 and TBR3 occurred between theI-A andI-E subregions. In both cases, theH-2K andI-A subregions were derived from theH-2 ^t1 chromosome, while theI-E, S andH-2D regions were derived from theH-2 ^b chromosome (K ^s A ^k E ^b S ^b D ^b ). TheH-2 ^a2 chromosome resulted from a crossover event between theH-2 ^a1 andH-2 ⁱ⁹ chromosomes. Ia and Ss typing of AIR1 suggested that theK toI-E regions originated fromH-2 ^a1 and theS andD regions originated fromH-2 ⁱ⁹ (K ^k A ^k E ^k S ^b D ^d ).     

Molecular characterization of meiotic recombination within the major histocompatibility complex of the mouse: Mapping of crossover sites within theI region

The molecular analysis of crossing-over within the mouse major histocompatibility complex provides a useful approach for the study of the structural characteristics of meiotic recombination. In this study five intra-I-region recombinants, each derived fromI ^k/I ^b heterozygotes, were characterized for restriction-fragment length polymorphisms (RFLPs) characteristic of theI region of the two parental strains. Southern blot analysis of intra-I recombinant strains A.TBR2, A.TBR3, A.TBR5, A.TBR13, and A.TBR17 using sixI-region DNA probes revealed that the point of crossing-over in all five recombinants occurred within a 6.2-kbKpnI-EcoRI segment located within theE gene. The segments of DNA containing the crossover point from each of the recombinant chromosomes were cloned by screening partial genomic libraries constructed in gt7 bacteriophage. Construction of partial restriction maps of the cloned segments from the parental and recombinant chromosomes permitted the boundaries of the area containing the crossover site to be narrowed to a 4.0-kb segment located almost entirely within an intron of theE gene. The recognition that the points of crossing-over in all five recombinants studied are clustered in a relatively small area of theI region provides further evidence for a hot spot of recombination associated with theE _ß gene.This work was supported by Grants AI14424 and AI20317 from the National Institutes of Health. J. Kobori was supported by a postdoctoral fellowship from the Arthritis Foundation. E. Zimmerer was supported by a postdoctoral fellowship from the Charles and Johanna Busch Fund of the Bureau of Biological Research. D. Spinella was supported by a predoctoral fellowship from the Charles and Johanna Busch Fund.     

Genetic control of contact sensitivity in mice: Effect ofH-2 and nonH-2 loci

The genetic control of delayed-type hypersensitivity in mice was investigated by contact sensitization with picryl chloride. Distribution patterns of contact sensitivity in 11 inbred strains of mice showed significant differences among strains. Comparison of levels of response between congenic-resistant lines and their inbred partners, at 9 to 11 weeks of age, revealed a clear association betweenH-2 haplotype and the magnitude of response. Testing ofH-2 recombinants further suggested the influence of two genes mapping at either end of theH-2 complex. While theH-2K ^d andH-2D ^k alleles were associated with a high response, theH-2K ^k ,H-2K ^b ,H-2D ^d , andH-2D ^b alleles were associated with a low response. Analysis of the ontogeny of response suggested that theH-2 haplotype manifests its effect through the maturation of contact sensitivity. On both the C57BL/6By and C57BL/10Sn backgrounds, theH-2 ^d haplotype was associated with early maturation of response, while theH-2 ^b haplotype was associated with late maturation. Analysis of the response of congenic lines with different genetic backgrounds and of CXB recombinant-inbred lines further revealed the marked effects of yet other genes on this trait.     

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.     

Analysis of theD-region products ofH-2444using monoclonal antibodies reveals the expression of a new class I-like molecule

To analyze how many D-region-encoded molecules could be detected inH-2 ^q , we produced a panel of nine monoclonal antibodies from AKR (K^kD^k) anti-AKR.M (K^kD^q) immunizations. All of the D_q region antibodies cross-reacted on D^d and/or L^d, and all except one cross-reacted on D^b, confirming the previously observed serologic and amino acid sequence homology between theD-region products ofH-2 ^d ,H-2 ^b , andH-2 ^q . All of these monoclonal antibodies precipitated 46 000 dalton molecules from both cell-surface-labeled and biosynthetically labeled BIO.AKM spleen cells, indicating that all were reactive with class I-like molecules. Sequential immunoprecipitation analysis with one of these antibodies, 66-3-5, reveals the presence of a previously unidentified class I-like molecule. Tryptic peptide map analysis reveals that this molecule may be the product of a newly describedH-2D ^q -region gene.     

H-2 effects on cell-cell interactions in the response to single non-H-2 alloantigens

Immune response (Ir) genes mapping in theI region of the mouseH-2 complex appear to regulate specifically the presentation of a number of antigens by macrophages to proliferating T cells. We have investigated the possibility that similarIr genes mapping in theH-2K andH-2D regions specifically regulate the presentation of target antigens to cytotoxic effector T cells. We report that the susceptibility of targets expressing specific non-H-2 H alloantigens to lysis by H-2-compatible, H-antigen-specific cytotoxic effector T cells is controlled by polymorphicH-2K/D genes. This control of susceptibility to lysis is accomplished through what we have defined operationally as antigen-specific regulation of non-H-2 H antigen immunogenicity. High immunogenicity of the H-4.2 alloantigen is determined by a gene mapping in theH-2K region ofH-2 ^b . However, high immunogenicity of H-7.1 is determined by a gene mapping in theH-2D region ofH-2 ^b . High immunogenicity of the H-3.1 alloantigen is determined by genes mapping in both theH-2K andH-2D regions ofH-2 ^b . Therefore, genes mapping in theH-2K andH-2D regions serve a function in presenting antigen to cytotoxic effector T cells. This function is analogous to that played byI-regionIr genes expressed in macrophages which present antigen to proliferating T cells. We present arguments for classification of theseH-2K/D genes as a second system ofIr genes and discuss the implications of twoH-2-linkedIr-gene systems, their possible functions, and their evolution.     

H-2 antigen variants in a cultured mouse leukemia cell line

We have investigated the effect of immune selection against a single gene product on a cultured mouse Friend leukemia cell line. The clonal cell line used is heterozygous at theH-2 complex and expresses theH-2 ^d andH-2 ^b haplotypes. The genes selected against were theH-2K locus alleles. Variants were obtained after a single-step selection using either antiH-2K^b or anti-H-2K^d serum. The phenotypes of the variants obtained showed an interesting asymmetry between the two haplotypes. Selection against theH 2K ^b allele resulted in the isolation of the two expected types of variant-those that had lost only H-2K^b and those that had lost both H-2K^b and the linked H-2D^b. Selection against H-2K^d yielded, exclusively, variants that had lost both the selected antigen and the linked H-2D^d. None of the variants showed an alteration in expression of antigens intrans configuration. Karyotypic analyses of the variants revealed that all the cells had retained both copies of chromosome 17 present in the wild-type cells. The results suggest that the variants did not emerge through chromosome loss.     

Expression of the H-Y Antigen on thymus cells and skin: Differential genetic control linked toK end ofH-2

The strength of the H-Y antigen on thymus cells and on skin was compared in differentH-2-congenic mouse strains using a host-versus-graft reaction popliteal lymph node assay, and skin grafts from males of parental strains grafted to F₁ hybrid females. The results revealed considerable differences in the strength of the H-Y antigen among different congenic strains; these differences demonstrate the effect of theH-2-linked gene on the expression of the H-Y antigen. The linkage withH-2 was also confirmed in tests with segregating F₂ generations. In the strains bearing recombinantH-2 haplotypes, the strength of the H-Y antigen is similar to that of parental strain from which the recombinant received itsK end, and the responsible gene (or genes) map to the left ofI-C. The effect of theH-2-linked gene(s) on thymus cells and skin is different. The gene linked to theK end ofH- 2^b determines a strong H-Y antigen on thymus cells, but a relatively weak H-Y antigen on skin. The gene linked to theK end ofH- 2^k determines a weak H-Y antigen on thymus cells, but a strong H-Y antigen on skin. The gene linked to theK end ofH- 2^d determines a weak H-Y antigen on both thymus cells and skin. Our observations raise the possibility that the structural gene for the H-Y antigen is linked toH-2. Alternative (but not exclusive) explanations invoke regulatory effects ofH-2 on the expression of the H-Y antigen, possibly by means of the control of the cellular andogen receptors.     

The role ofH-2 regions in overcoming tissue incompatibility

Neonatal transplantation tolerance to the products of theH-2 ^b complex was induced in B10.A (H-2 ^a ) mice. On the basis of the survival of skin allografts it was found that antigens determined by theD region of theH-2 ^b complex (of the B10.A(2R) strain) were most easily overcome and that tolerance to the products of theD end of theH-2 complex (of the B10.A(4R) strain) was also easy to induce. The antigens produced by theK end ofH-2 (of the B10.A(5R) and B10.A(3R) strains) represented a stronger incompatibility barrier and a difference in the entireH-2 ^b complex caused strongest resistance to tolerance induction. When tolerance to the products of the entireH-2 ^b complex was induced in newborn B10.A mice, and the neonatally treated animals were grafted simultaneously with five different grafts, those disparate at theK end ofH-2 and in the entireH-2 region were rejected in some animals, while the grafts disparate at theD end of H-2 remained intact in the same mice. No dependence on theI-J subregion was observed in this system. Furthermore, tolerance was more easily inducible in male than in female B10.A mice.     

Effects of fourH-2K mutations on virus-induced antigens recognized by cytotoxic T cells

Lysis of ectromelia- or LCM virus-infected macrophage target cells by virus-specific cytotoxic T cells from mice immunized with the homologous virus occurred only where donors of T cells and target cells shared eitherH-2K orH-2D genes. With both viruses, use of T cell or target cell donors bearing mutations (B6.C-H-2^ba, B6-H-2^bh, B6-H-2^bg1, and B6-H-2^bg2), all of which apparently occurred in the same single genetic element in theH-2K^b region, abolished (H-2^ba) or impaired (H-2^bh,H-2^bg1 andH-2^bg2) lysis in T cell-target cell combinations that shared (apart from the mutations) all other genes in theK, I-A, orI-B regions of theH-2 complex. The data suggest that virus-induced antigenic patterns on infected B6.C-H- 2^ba (mutant) cells are more different antigenically from those on C57BL/6 (wild type) cells than are those on infected cells from the other mutants -B6-H-2^bh, B6-H-2^bg1, and B6-H-2^bg2. (B6.C-H-2^ba× B6 -H-2^bh)F₁ mice behaved like B6-H-2^bh, indicating no complementation, and confirming that theH-2K gene(s) involved in recognition of virus-infected cells by virus-specific T cells behave as a single element. These findings are discussed in relation to the nature of virus-induced antigenic patterns that are recognized by virus-specific cytotoxic T cells.     

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     

Characterization of a TL−variant of a homozygous TL+ mouse lymphoma

A homozygous antigen-loss variant for the TL antigen was isolated by immunoselectionin vitro. The variant expressed <0.01 the parental amount of TL antigen on its surface as measured by quantitative absorption. Neither theK nor theD end H-2^k antigens were detectable on the surface of the variant, although parental amounts of Thy 1.2 and GCSA were expressed. Karyotypic analysis showed that the variant had one less chromosome than the parental line.     

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.     

Serological characterization of previously unknown H-2 molecules identified in the products of theK d andD k region

The molecular relationship between H-2 private and some public specificities was studied in C3H.OH (H-2 ⁰² ) mice using surface-antigen re-distribution methods. Besides the K^d- and D^k-region antigens, which can be capped by antisera against the private and public specificities characteristic for a given allele, a previously unknown type of molecule was found in the products of both theK ^d andD ^k regions. These can be capped by the respective anti-private serum but not by antisera against some public specificities. The two K^d-region molecules are provisionally named H-2K1^d and H-2K2^d. We detected them onH-2 ⁰² (K ^d ,I ^d ,S ^d ,D ^k ) and also onH-2 ^dx (K ^d ,I ^f ,S ^f ,D ^dx ) T lymphocytes. Similarly, the two types of molecules detected on the products of theD ^k region are provisionally named H-2D1^k and H-2D2^k. The serological characteristics of these molecules are described. When compared with the products of theD ^d region, in which we previously described three different molecules (H-2D^d, H-2M^d, and H-2L^d), the mutual relationship between H-2K1^d and H-2K2^d as well as between H-2D1^k and H-2D2^k appears to be similar to that between H-2D^d and H-2M^d. In the absence of relevant recombinants or informative biochemical data, it is, however, difficult to establish homology between molecules produced by differentK- andD-region alleles.     

Serological and complementation studies in four C57BL/6H-2 mutants

C57BL/6 (H-2 ^b ) mice, and four mutants (B6.C-H-2 ^ba , B6-H-2 ^bg1 , B6-H-2 ^bg2 , B6-H-2 ^bh ) derived from this strain after separate mutations had occurred at the same locus within theH-2 complex, were analyzed to determine whether the mutations had led to anyH-2 (or Ia) difference which could be detected serologically. The strains were typed directly with antisera specific for H-2K and H-2D public and private specificities and for the Ia specificities; quantitative absorption studies were also performed for the relevant H-2K^b, H-2D^d and Ia^b specificities. In no case was any quantitative or qualitative difference detected serologically between any of the strains. In addition, by using a variety of techniques to produce and assay for antibody, we failed to produce any antisera between the parental strains and the four mutants. TheH-2 mutations therefore appear to give rise to a type of antigenic specificity which is recognized byT cells and which generateT, but notB cell responses; nor are they recognized by H-2 or Ia alloantisera. The location of the mutating locus within theH-2 complex was shown by the complementation method to be within theK orIA region and not in theIB region, since crosses of the mutant strains with B10.A(4R) or D2.GD failed to complement for a subsequent C57BL/6 skin graft.     

The histocompatibility-2 system in wild mice

The I-region gene products of 29 wild-derivedH-2 haplotypes on a B10 background (B10.W congenic lines) were typed with alloantisera which detect 17 inbred I-region antigens. Five new I-region antigens were defined by expanding the inbred line panel ofH-2 haplotypes to includeH-2 ^u , H-2^v, andH-2 ^j . Based on serological analyses of the inbred and B10.W lines, the polymorphism of theIA gene (or genes) is estimated to be at a minimum of 15 alleles and theIE gene (or genes) at a minimum of 4 alleles. These results indicate that theIA subregion is more polymorphic than theIE subregion. By combining the I-region typing data with theH-2K andH-2D region typing data reported previously, a total of 11 new natural recombinants of inbredH-2 alleles were detected among the B10.W lines.     

Detection of two allotype-(Ig-1)-linked minor histocompatibility loci by the use ofH-2-restricted cytotoxic lymphocytes in congenic mice

Cytotoxic lymphocytes (CTL) were generated betweenIg-1-congenic strains BALB/c(H-2^d,Ig-1^a) andC.B-17(H-2^d,Ig-1^b) by cross-immunization in both directions and rechallenge in vitro. The effector cell populations specifically lysed target cells sharing both theH-2 haplotype and theIg-1 allele of the sensitizing strain. B- and T-cell blasts were equally good targets, suggesting thatH-2-restricted cytotoxic lymphocytes are not directed against serologically defined conventional allotypic determinants, but probably against minor histocompatibility antigens controlled by genes linked to theIg-1 complex. Competition experiments using cold target cells from a series ofIg-1^b-congenic strains of the BALB/c background (BAB-14, C.B-17, C.B-26) revealed two not yet described minor histocompatibility loci linked to theIg-1 complex: We could demonstrate that BALB/c anti-C.B-17 effector cells recognize at least two distinct antigenic determinants on C.B-17 target cells, but only one on target cells from BAB-14, which carries a recombinantIg-1 complex. From these results we conclude that one of the minor histocompatibility antigens, designated as H(C_H), is encoded by a gene linked to the heavy-chain constant-region (C_H) genes, whereas the second minor histocompatibility antigen, designated as H(V_H), is coded for by a gene linked to the heavy-chain variable-region (V_H) genes. These two new genetic markers may be useful for further analysis of the mouseIg-1 complex because the analysis of the H(C_H) and H(V_H) genes may facilitate the search for recombinants in that chromosomal region.     

The complete amino acid sequence of the murine transplantation antigen H-2Db as deduced by molecular cloning

A mouse cDNA library derived from the EL4 cell line (b-haplotype) was screened with a probe containing a small part of the H-2K^b coding region. One of the clones isolated, pH203, encodes a protein whose deduced amino acid sequence is identical with the known sequence of H-2D^b in 141 of 141 positions available for comparison. The clone, therefore, is believed to code for the H-2D^b transplantation antigen. The cDNA insert of pH203 contains the coding region for residues 82 through the carboxy-terminus of H-2D^b, and includes 476 nucleotides of the 3-untranslated sequence. Comparison between the H-2D^b cDNA clone and a previously isolated H-2K^b cDNA clone shows homologies of 83% and 91% at the amino acid and nucleotide levels, respectively. Analysis of DNA sequences at the 3-coding and untranslated regions suggests that the mRNAs of H-2K^b and H-2D^b are spliced differently at their 3-coding ends.     

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.     

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.