Radbruch A, Liesegang B, Rajewsky K
Proc Natl Acad Sci U S A. 1980 May;77(5):2909-13. doi: 10.1073/pnas.77.5.2909.
We have used fluorescence-activated cell sorting with class-specific antisera to isolate spontaneous variants in the expression of immunoglobulin heavy chain class from the mouse myeloma cell line X63 (IgGI, kappa). In the wild-type cell population, only one type of variants was found, namely, cells expressing IgG2b. From an IgG2b variant clone we isolated secondary variants that had either reverted to IgGI expression or expressed IgG2a or IgG2a and IgG2b concomitantly. The variant heavy chains are of normal size. The variant immunoglobulins were characterized serologically, and all of them still expressed the wild-type idiotype. Wild-type and variant cell populations were screened for heavy chain class-switch variants by fluorescence microscopy. A variety of switch variants was found in addition to the ones isolated by cell sorting, and a clear pattern of class switching (gamma 1 leads to gamma 2b leads to gamma 2a leads to alpha) with frequent reversion emerges from this analysis. Cells expressing new heavy chain classes occurred at frequencies of about 10(-7)-10(-6)/cell per generation, whereas revertants were as frequent as 10(-6)-10(-5)/cell per generation.
我们使用荧光激活细胞分选技术，结合类特异性抗血清，从小鼠骨髓瘤细胞系X63（IgG1，κ）中分离出免疫球蛋白重链类表达的自发变体。在野生型细胞群体中，仅发现一种变体类型，即表达IgG2b的细胞。从一个IgG2b变体克隆中，我们分离出了二级变体，这些变体要么回复到IgG1表达，要么同时表达IgG2a或IgG2a和IgG2b。变体重链大小正常。对变体免疫球蛋白进行了血清学表征，所有变体仍表达野生型独特型。通过荧光显微镜对野生型和变体细胞群体进行重链类转换变体筛选。除了通过细胞分选分离出的变体之外，还发现了多种转换变体，并且从该分析中出现了一种明确的类转换模式（γ1转换为γ2b，γ2b转换为γ2a，γ2a转换为α），且频繁发生回复。表达新重链类别的细胞出现频率约为每代每细胞10^(-7)-10^(-6)，而回复体的频率高达每代每细胞10^(-6)-10^(-5)。
