Function and disease susceptibility of bovine MHC class II molecule

为了探讨牛淋巴细胞抗原(BOLA)基因的多态性与BLV诱导的淋巴瘤抗性或易感性的关系，从54只BLV感染的健康、持续性淋巴细胞增多症和淋巴瘤3个独立阶段的动物中克隆了高度多态的BOLA-DRB3基因外显子2，并测定了其核苷酸序列。序列分析表明，编码Val基因第78位的BOLA-DRB3等位基因可能与BLV诱导的淋巴瘤耐药有关。编码Val的等位基因由Arg或Lys和Glu组成，Arg或Lys代表第71位的正电荷，Glu代表第74位的负电荷。接下来，为了证实MHCⅡ类基因多态性与白血病的关系，我们感染了28只绵羊。在16只患淋巴瘤的绵羊中，38%的绵羊携带绵羊白细胞抗原(OLA)-DRB1 Arg^&lt；70&gt；-Lys^&lt；71&GT；(RK)等位基因，而在12只感染BLV的绵羊中，RK的携带率为83%。为了分析绵羊OLA-DRB1 RK等位基因的免疫反应，我们用合成的BLV囊膜糖蛋白GP 51的T辅助、T细胞毒性和B细胞表位的多个抗原肽的混合物免疫RK/X或X/X基因型的绵羊，并在最后一次免疫后2周用BLV感染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，未发生白血病。我们的结果表明，免疫应答的不同是由于MHC II类等位基因的不同而导致的，并与BLV诱发白血病的风险有关。

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.