Maturation of xenoantibody gene expression during the humoral immune response of rats to hamster xenografts.
Maturation of xenoantibody gene expression during the humoral immune response of rats to hamster xenografts.
复制标题
大鼠对仓鼠异种移植物的体液免疫反应期间异种抗体基因表达的成熟。
DOI：
10.1034/j.1399-3089.2001.00136.x
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Cramer,DV
中科院分区：
文献类型：
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作者：
Wu,GD;Gochi,E;Jin,YS;Swensson,J;Starnes,VA;Cramer,DV
翻译后摘要：免疫球蛋白同种型转换代表抗体成熟的体液免疫反应的发展中的一个重要组成部分。我们最近进行了一系列的研究，在非免疫抑制的啮齿动物模型，以确定异种抗体的生产动力学，并寻求异种抗体IG基因表达的异种移植受体的成熟的证据。用仓鼠心脏异种移植物移植LEW大鼠，并使移植物保持原位以延长宿主的免疫刺激。在移植后第4、8、21、28和40天检查抗仓鼠抗体。在移植后第4天和第21天，从异种移植物受体的B淋巴细胞构建大鼠μ或γ重链特异性cDNA文库。对来自各组的编码IG VHHAR基因家族的所选cDNA克隆进行测序并分析体细胞突变的存在。我们发现，用流式细胞术检查的异种抗体的反应性经历了连续的变化，其中IgM滴度在移植后第8天（PTx）达到峰值，并在21天后恢复到低水平。 IgG滴度在PTx约一周时开始增加，并在21-28天达到峰值。 所有IgG同种型（IgG 1、2a、2b和2c）均不同程度地参与IgG应答。血清被动转移实验表明，在移植后第4天从血清中分离的IgM抗体组分能够引起仓鼠异种移植物的超急性排斥反应（HAR），而第21-40天的IgM组分未能引起HAR（N= 7，MST = 4天），这种模式与移植后第4-8天总异种反应性IgM水平升高和第21天降至低水平一致。 从第21-40天抗血清中分离的含IgG的级分引起HAR（N= 7，MST = 36 min），而来自第8天血清的IgG级分未能诱导移植物排斥。 对10个cDNA克隆的VH基因重排的遗传分析表明，IG μ（n= 5）和γ（n= 5）链克隆使用相同的VH基因家族（VHHAR家族）编码其抗体结合活性。 大多数（80%）的IgM克隆存在于其原始生殖系配置。相比之下，IgG克隆的核苷酸序列显示IG重链基因CDR区的置换突变数量增加，这为体细胞突变在IgG异种抗体应答成熟中的潜在作用提供了证据，因为体液应答在移植后随时间成熟。
Abstract:Immunoglobulin isotype switching represents an important component of antibody maturation in the development of humoral immune responses. We have recently conducted a series of studies in a nonimmunosuppressed rodent model to define the kinetics of xenoantibody production and seek evidence for the maturation of xenoantibody Ig gene expression by xenograft recipients. LEW rats were transplanted with hamster cardiac xenografts and the grafts were allowed to remain in situ for prolonged immune stimulation of the host. Anti‐hamster antibodies were examined at days 4, 8, 21, 28 and 40 post‐transplantation. cDNA libraries specific for rat µ or γ heavy chains were constructed from B lymphocytes of the xenograft recipients at day 4 and day 21 post‐transplantation. Selected cDNA clones encoding the Ig VHHAR family of genes from each group were sequenced and analyzed for the presence of somatic mutations. We found that the reactivity of xenoantibodies examined with flow cytometry underwent sequential changes in which IgM titers peaked at day 8 post‐transplantation (PTx) and returned to low levels after 21 days. IgG titers started to increase at about one week PTx and peaked at 21–28 days. All the IgG isotypes (IgG1, 2a, 2b and 2c) were differentially involved in the IgG responses. Serum passive transfer experiments demonstrated that IgM antibody fractions separated from sera at day 4 post‐transplantation were capable of causing hyperacute rejection (HAR) of hamster xenografts, whereas IgM fractions from days 21–40 failed to cause HAR (N= 7, MST = 4 days), a pattern that was consistent with a rise in total xenoreactive IgM levels at days 4–8 and a fall to low levels at 21 days post‐transplantation. IgG‐containing fractions separated from day 21–40 antisera caused HAR (N= 7, MST = 36 min) whereas IgG fractions from day 8 sera failed to induce graft rejection. Genetic analysis of the rearranged VHgenes from 10 cDNA clones demonstrated that the Ig µ (n= 5) and γ (n= 5) chain clones used the same family of VHgenes (VHHAR family) to encode their antibody binding activity. The majority (80%) of the IgM clones were present in their original germline configuration. In contrast, the nucleotide sequences from IgG clones manifested an increase in the numbers of replacement mutations in the CDR region of the Ig heavy chain genes, providing evidence for a potential role for somatic mutation in the maturation of IgG xenoantibody responses as the humoral response matures with time post‐transplantation.