Castigli E, Alt F W, Davidson L, Bottaro A, Mizoguchi E, Bhan A K, Geha R S
Division of Immunology, Children's Hospital, Boston, MA.
Proc Natl Acad Sci U S A. 1994 Dec 6;91(25):12135-9. doi: 10.1073/pnas.91.25.12135.
To study the role of B-cell antigen CD40 in immune responses, mouse embryonic stem (ES) cells in which both copies of the gene encoding CD40 had been disrupted by homologous recombination were injected in RAG-2 (recombination-activating gene-2)-deficient blastocysts to generate chimeras in which all mature lymphocytes are derived from the CD40-deficient ES cells. T- and B-cell number and phenotype were normal in the CD40-/- chimeras. However, B cells failed to proliferate and undergo isotype switching in vitro in response to soluble CD40 ligand (sCD40L) with interleukin 4 (IL-4) but responded normally to lipopolysaccharide (LPS) with IL-4. CD40-/- chimeras completely failed to mount an antigen-specific antibody response or to develop germinal centers following immunization with the T cell-dependent (TD) antigen keyhole limpet hemocyanin. In contrast, CD40-/- mutant mice responded normally to the T cell-independent (TI) antigens, 2,4,6-trinitrophenyl (TNP)-LPS and TNP-Ficoll. The most noticeable alteration in the serum immunoglobulin levels of young (6-8 weeks old) CD40-/- animals was absence of IgE and severe decrease of IgG1 and IgG2a. These results confirm the essential role of CD40- CD40L interactions in the antibody response to TD antigens and in isotype switching.
为研究B细胞抗原CD40在免疫反应中的作用，将编码CD40的基因的两个拷贝均通过同源重组而被破坏的小鼠胚胎干细胞（ES细胞）注射到RAG-2（重组激活基因-2）缺陷的囊胚中，以产生嵌合体，其中所有成熟淋巴细胞均源自CD40缺陷的ES细胞。在CD40基因敲除的嵌合体中，T细胞和B细胞的数量及表型均正常。然而，B细胞在体外对可溶性CD40配体（sCD40L）与白细胞介素4（IL-4）的反应中无法增殖且不能进行同种型转换，但对脂多糖（LPS）与IL-4的反应正常。在用T细胞依赖性（TD）抗原钥孔戚血蓝蛋白免疫后，CD40基因敲除的嵌合体完全无法产生抗原特异性抗体反应或形成生发中心。相比之下，CD40基因敲除的突变小鼠对T细胞非依赖性（TI）抗原2,4,6-三硝基苯（TNP）-LPS和TNP-菲可正常反应。年轻（6至8周龄）的CD40基因敲除动物血清免疫球蛋白水平最显著的改变是缺乏IgE以及IgG1和IgG2a严重降低。这些结果证实了CD40-CD40L相互作用在对TD抗原的抗体反应和同种型转换中的重要作用。
