Vernino L A, Pisetsky D S, Lipsky P E
Harold C. Simmons Arthritis Research Center, University of Texas Southwestern Medical Center, Dallas 75235.
Cell Immunol. 1992 Jan;139(1):185-97. doi: 10.1016/0008-8749(92)90111-2.
B cells expressing the CD5 marker in the mouse have been suggested to be a separate lineage and a major source of autoantibody production. In man, this relationship is less clear. Studies were therefore undertaken to determine whether human CD5+ B cells represent a distinct lineage of cells that differ in patterns of antibody production from CD5- B cells. In normal B cell populations, CD5 was expressed by a mean of 24.0 +/- 2.8% (n = 10) of CD20+ B cells. Of note, an increased frequency of CD5+ B cells was not found in patients with systemic lupus erythematosus (mean of 17.9 +/- 2.8%, n = 16). Analyzing CD5+ B cells for cell membrane Ig isotype expression demonstrated similar frequencies of IgG and IgA expressing cells as were found on the CD5- B cell population, although the frequency of IgM+ cells was slightly increased. Incubation of CD20+ B cells with phorbol myristate acetate (PMA) for 72 hr increased the frequency of CD5 expressing B cells by more than threefold. CD5 expression was also increased by coculture with anti-CD3-activated T cells and most markedly by simultaneous stimulation with both PMA- and anti-CD3-activated T cells (greater than 50% positive). Analysis of CD5- B cells clearly indicated that stimulation with PMA or anti-CD3-activated T cells induced the majority to become CD5+ transiently. Functional analysis of Ig production by CD5+ and CD5- B cells stimulated with anti-CD3-activated T cells indicated that both populations in normals produced IgM and a variety of autoantibodies in comparable amounts, whereas the CD5- B cells produced greater quantities of IgG. B cells were activated with anti-CD3-stimulated T cells followed by separation into CD5+ and CD5- populations. The largest amount of Ig was produced by CD5- B cells that were induced to express CD5, although all populations produced some Ig. These data suggest that CD5 behaves as an activation marker on human B cells rather than as a marker for a distinct lineage of cells. Moreover, CD5 expression does not appear to identify a population of resting B cells with a greater capacity to produce antibodies to DNA or other autoantibodies.
在小鼠中，表达CD5标志物的B细胞被认为是一个独立的谱系，也是自身抗体产生的主要来源。在人类中，这种关系尚不清楚。因此开展了研究，以确定人类CD5⁺ B细胞是否代表了一个与CD5⁻ B细胞在抗体产生模式上不同的独特细胞谱系。在正常B细胞群体中，平均有24.0±2.8%（n = 10）的CD20⁺ B细胞表达CD5。值得注意的是，系统性红斑狼疮患者中未发现CD5⁺ B细胞频率增加（平均值为17.9±2.8%，n = 16）。分析CD5⁺ B细胞的细胞膜Ig同种型表达发现，表达IgG和IgA的细胞频率与CD5⁻ B细胞群体中的相似，尽管IgM⁺细胞的频率略有增加。用佛波醇肉豆蔻酸酯乙酸酯（PMA）孵育CD20⁺ B细胞72小时，使表达CD5的B细胞频率增加了三倍多。与抗CD3激活的T细胞共培养也会增加CD5的表达，而同时用PMA和抗CD3激活的T细胞刺激时增加最为明显（阳性率大于50%）。对CD5⁻ B细胞的分析清楚地表明，用PMA或抗CD3激活的T细胞刺激会诱导大多数细胞短暂地变为CD5⁺。对用抗CD3激活的T细胞刺激的CD5⁺和CD5⁻ B细胞的Ig产生进行功能分析表明，正常情况下这两个群体产生的IgM和各种自身抗体数量相当，而CD5⁻ B细胞产生的IgG量更多。用抗CD3刺激的T细胞激活B细胞，然后将其分离为CD5⁺和CD5⁻群体。诱导表达CD5的CD5⁻ B细胞产生的Ig量最大，尽管所有群体都产生了一些Ig。这些数据表明，CD5在人类B细胞上表现为一种激活标志物，而不是一个独特细胞谱系的标志物。此外，CD5的表达似乎并不能识别出一群具有更强产生抗DNA抗体或其他自身抗体能力的静息B细胞。
