Function and disease susceptibility of bovine MHC class II molecule

为了研究牛淋巴细胞抗原（BoLA）基因多态性与blv诱导的淋巴瘤的抗性或易感性之间的关系，从54只blv感染动物中克隆出高度多态性的BoLA- drb3基因外显子2，并测定其核苷酸序列。序列分析显示，编码Val的BoLA-DRB3等位基因78位可能与blv诱导淋巴瘤的抗性有关。编码第78位Val的等位基因由Arg或Lys（在第71位表示正电荷）和Glu（在第74位表示负电荷）表征。相比之下，编码第78位Tyr的等位基因具有Ala、Asn或Tyr等氨基酸，这些氨基酸在第74位代表中性电荷，与淋巴瘤易感性相关。接下来，为了证实MHCⅱ类基因多态性与白血病的关系，我们用BLV感染了28只羊。在16只淋巴瘤羊中，38%携带羊白细胞抗原(OLA)-DRB1 Arg^<70>-Lys^<71> (RK)特异性等位基因，而在12只无症状期blv感染的羊中，这一比例为83%。为了分析OLA-DRB1 RK等位基因对绵羊的免疫反应，我们用BLV包膜糖蛋白gp 51的t辅助抗原、t细胞毒性抗原和b细胞表位抗原合成多肽的混合物对携带RK/X基因型或X/X基因型的绵羊进行免疫，并在最后一次免疫后两周，用BLV感染的绵羊的血液攻击所有绵羊。携带抗性等位基因的绵羊对混合多肽表现出较高的免疫应答，没有发生白血病。我们的研究结果表明，免疫应答的差异是由MHC II类等位基因的差异引起的，并与blv诱导的白血病发生的风险有关。

To investigate the relationship between polymorphism of bovine lymphocyte antigen (BoLA) gene and resistance or susceptibility to BLV-induced lymphoma, exon 2 of the BoLA-DRB3 gene which is highly polymorphic was cloned from 54 BLV-infected animals with 3 independent stages such as an aleukemic healthy, persistent lymphocytosis and lymphoma, and the nucleotide sequences were determined. Sequence analysis revealed that the BoLA-DRB3 alleles encoding Val at position 78 may be associated with resistance to BLV-induced lymphoma. Alleles encoding Val at position 78 were characterized by Arg or Lys, which represent a positive charge at position 71 and by Glu, which represents a negative charge at position 74. By contrast, alleles encoding Tyr at position 78, have amino acids such as Ala, Asn or Tyr, which represent a neutral charge at position 74 and were associated with susceptibility to lymphoma.Next, to confirm the association between polymorphism of MHC class II gene and leukemia, we infected 28 sheep with BLV.Among the 16 sheep with lymphoma, 38% carry specific alleles of the ovine leukocyte antigen (OLA)-DRB1 Arg^<70>-Lys^<71> (RK) as compared to 83% among the 12 BLV-infected sheep at the asymptomatic stage. To analyze the immunoreaction of sheep with allele of OLA-DRB1 RK, we immunized sheep carrying either a RK/X genotype or a X/X genotype with a mixture of synthetic multiple antigenic peptides of T-helper, T-cytotoxic, and B-cell epitopes of BLV envelope glycoprotein gp 51, and two weeks after the last immunization, all sheep were challenged with blood from a BLV-infected sheep. Sheep carrying resistant allele showed high immunoresponse against the mixed peptides and did not proceeded to ieukemia. Our results indicate that difference of immunoresponse resulted due to difference of MHC class II alleles and involved the risk of BLV-induced leukemogenesis.