Locus-specific cDNA cloning in the class I multigene family: structure of H-2Dr and H-2Ds

Low expression of a Ddm7/Ldm7-hybrid mutant (D/Ldm7) in the novel haplotype H-2nc identified in atopic dermatitis model NC/Nga mice

Environmental factors and the major histocompatibility complex (MHC) are involved in the pathogenesis of atopic dermatitis (AD). However, MHC type (H2 haplotype) of AD model mice NC/Nga is poorly understood. Alloreactive CD8⁺ or CD4⁺ T cells in NC/Nga strongly responded to each antigen-presenting cells (A/J: H-2^a, C57BL/6: H-2^b, BALB/c: H-2^d, or C3H/HeJ: H-2^k), suggesting that NC/Nga has other H2 haplotype. Polymorphic microsatellite (CA)ⁿ repeats in TNF-α gene differ based on the H2 haplotype at present. NC/Nga's (CA)ⁿ repeats (n = 19) were different from other examined strains, A/J (n = 14), BALB/c (n = 14), C3H/HeJ (n = 16), and C57BL/6 (n = 20). Using flow cytometry and genotyping, we demonstrated the NC/Nga H2 haplotype had a unique phenotype (K^d, I-A^k, and I-E^k) in which D^d and L^d lacked as protein despite sensitive mRNA detection. The loss of D^d and L^d was caused by forming a unique D^dm7/L^dm7-hybrid mutant (D/L^dm7). We propose to call this novel H2 haplotype the "H-2^nc," and provide the important information regarding the AD research using NC/Nga mice.

Conservation of the H-2 BF1 binding motif 5' of the H-2Ds, Ks and Dq genes

The biological consequences of radiation leukaemia virus (RadLV) infection include the stimulation of H-2 antigen expression soon after injection of the virus. Early studies demonstrated that resistance to RadLV-induced leukaemia in certain mouse strains is mediated by genes in the H-2D region of the major histocompatibility complex (MHC). Recent studies have shown that elevated H-2Dd expression on the thymocyte cell surface of resistance mouse strains results from increased mRNA transcription and is correlated with elevated levels of a DNA-binding activity that recognizes a short DNA sequence 5' of the start of transcription for the H-2Dd gene. This binding activity has been termed H-2 binding factor 1 (H-2 BF1) and is found exclusively in the thymus. In an effort to examine the H-2 genes of RadLV-susceptible mice for the presence of the H-2 BF1 binding target, we have cloned class I genes from the highly susceptible B10.S mouse strain and have identified both the Ds and the Ks genes. The entire genomic sequence for the Ds gene has been determined and is reported here. In addition, the 5' regulatory region of the previously cloned Dq gene has been sequenced; mice of the Dq haplotype are also susceptible to RadLV-induced leukaemia. In this report, we show that the H-2 BF1 DNA binding sequence is present 5' of each of these three class I genes.

Selective loss of H-2Ds antigen on a murine B lymphoma due to a post-transcriptional block in expression

The major histocompatibility (MHC) class I antigens are coordinately expressed in most cells. However, some tumors or virus-infected cells lack expression of one MHC class I antigen, while expression of the other MHC class I antigens is unaffected. We previously described the selective expression of MHC class I antigens on a B-cell lymphoma from SJL/J mice called RCS5. This tumor expresses H-2Ks, but has lost cell surface expression of H-2Ds. To understand the mechanism responsible for the selective loss of H-2Ds on the cell surface, we analysed H-2Ds mRNA and protein in the RCS5 tumor. Here we report that H-2Ds mRNA was expressed in RCS5, but H-2Ds protein was not detected in cell lysates. To determine whether the H-2Ds mRNA from RCS5 was able to direct the synthesis of H-2Ds protein, we performed cDNA cloning, in vitro translation and gene transfer experiments using a cell line related to RCS5 (cRCS-X). Our results indicated that the inhibition of H-2Ds expression in cRCS-X occurred after transcription of a non-defective H-2Ds mRNA. Furthermore, H-2Ds antigen expression was restored in cRCS-X using a retroviral vector to express the recombinant H-2Ds cDNA. These results indicate that the inhibition of H-2Ds expression could be overcome either by out competing an inhibitor that functions in trans or by removing cis-acting regulatory sequences from the endogenous H-2Ds mRNA.

Cross-reactivity among evolutionarily distant major histocompatibility complex class I molecules (HLA-B27 and H-2Kk) revealed by xenoreactive T lymphocytes

A set of mouse HLA-B27-reactive cytotoxic T lymphocyte clones were found to recognize the HLA-B27 molecule in an H-2-unrestricted manner, i.e. independently of any mouse major histocompatibility complex (MHC) molecule. The reactivity patterns of these clones on HLA-B27 variants (positive only on HLA-B*2702 and HLA-B*2701) allowed the identification of residues N77 and A81 of the HLA-B27 molecule as important for their reactivity. The location of these residues in the peptide-binding groove (specificity pocket F) suggested that the reactivity of the clones is dependent on HLA-B27-bound peptide(s). However, several other class I molecules sharing these residues (N77 and A81) were not recognized, indicating that other residues might also be involved. One of the clones was found to display an interesting cross-reactivity with allogeneic H-2Kk molecules, sharing N77 and A81 with HLA-B*2702. Sequence comparison suggested the involvement of residue H9, located in specificity pocket B of the peptide-binding groove, and revealed some similarity of pockets B in HLA-B27 and H-2Kk. The structural basis of such T cell-mediated MHC cross-reactions across species barriers is discussed.

Structural and functional analysis of three D/L-like class I molecules from H-2v: indications of an ancestral family of D/L genes

Three cDNA with D region gene features have been identified from the H- 2v haplotype. Provisionally, the sequences have been designated as D/Lv1, D/Lv2, and D/Lv3. The coding segments for the antigen binding domain (ABD) of all three D/Lv genes were engineered into a class I genomic expression vector and expressed in L cells. FACS analysis of the three D/Lv-Ld gene transfectants revealed that the D/Lv1 molecules were recognized by both monoclonal antibodies (mAbs) 141 and 142, and the D/Lv2 molecules were recognized by mAb 143. In addition to the D/Lv1 molecules, the mAb 141 also recognized the D/Lv3 molecules. Both the D/Lv1-Ld and D/Lv2-Ld transfectants were killed efficiently by H- 2Dv region-specific alloreactive CTL. The D/Lv3 gene is the first identified D region gene other than D and L that is transcribed abundantly in spleen and the D/Lv3 RNA is present as two alternatively spliced forms. Structural analysis of the D/Lv3 hybrid molecules showed that it was susceptible to proteolysis and thermolabile at 37 degrees C, suggesting D/Lv3 is a transcribed pseudogene. A parsimony tree analysis of three D/Lv sequences with a set of class I gene sequences revealed that the H-2v sequences clustered with D region genes. The presence of a third gene with D/L-like features in H-2v, yet structurally different from the known D/L alleles, raises the possibility that the current D/L genes evolved from a family of D/L- like genes, some of which are no longer represented among many of the mouse major histocompatibility complex haplotypes. The observation that D region alleles cluster into subgroups suggests that the alleles are not all related to each other by linear descent through a single locus. We propose that current alleles are derived from more than one ancestral locus in a manner similar to the origin of the gamma 2 a immunoglobulin constant region alleles.

Nucleotide sequence analysis of H-2Df and the spontaneous in vivo H-2Dfm2 mutation

The nucleotide sequence of the standard H-2Df allele and the spontaneous in vivo H-2Dfm2 mutation are reported here. Locus-specific sequences in the 5' and 3' untranslated regions of the mouse MHC class I H-2D-region genes were used to design primers for the specific amplification and cloning of H-2D-region cDNA from standard B10.M/Sn H-2f and mutant B10.M-H-2fm2/Mob mice. A partial Df genomic clone and direct Df and Dfm2 mRNA sequence analysis confirmed the authenticity of the cDNA clones. Interestingly, H-2Df contains a proline in the alpha-helix of the alpha 1 domain at amino acid position 62; no other known class I molecule has a proline at this position. The H-2Dfm2 mutation, however, replaces this unique proline in Df with the H-2 and HLA consensus arginine at position 62. Although a point mutation cannot be ruled out, the single nucleotide change in the H-2Dfm2 mutation is flanked by a stretch of 47 nucleotide bases with an identical counterpart in H-2Kf, a finding consistent with a recombinatorial event between H-2Kf and H-2Df.