Tohma S, Ramberg J E, Lipsky P E
Harold C. Simmons Arthritis Research Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
J Leukoc Biol. 1992 Jul;52(1):97-103. doi: 10.1002/jlb.52.1.97.
Interactions between intercellular adhesion molecule 1 (ICAM-1, CD54) and leukocyte function-associated antigen 1 (LFA-1, CD11a/CD18) play a critical role in T cell-B cell collaboration. The current experiments were carried out to determine the expression and distribution of these adhesion molecules on human peripheral T cells and B cells during T cell-B cell collaboration. Resting CD4+ T cells were largely ICAM-1 negative, whereas immobilized anti-CD3 monoclonal antibody (mAb) rapidly induced ICAM-1 expression. By contrast, most B cells expressed ICAM-1 before activation, and further increases in density were noted with stimulation. Both B cells and CD4+ T cells expressed LFA-1 before activation, although the density on CD4+ T cells was considerably greater. A double staining method for electron microscopic analysis was developed that permitted analysis of the expression and distribution of ICAM-1 to be assessed during T cell-B cell collaboration. Under the experimental conditions examined, B cells showed a uniform distribution of ICAM-1. In contrast, ICAM-1 was highly mobile on the surface of CD4+ T cells. If the T cells were not fixed, staining, even at 4 degrees C, caused rapid redistribution of ICAM-1 into aggregates. However, by fixing cells before the staining procedures, the distribution of ICAM-1 on CD4+ T cells could be accurately assessed. Most (85%) of the fixed activated CD4+ T cells showed a uniform distribution of ICAM-1. However, when activated CD4+ T cells were cocultured with B cells, redistribution of ICAM-1 on CD4+ T cells but not B cells occurred, such that the majority (85%) was found at or immediately adjacent to the point of attachment to the B cells. No redistribution of LFA-1 on either T cells or B cells was found. These findings suggest that rapid changes in density of ICAM-1 expression and the mobility of ICAM-1 on activated T cells may play a role in providing activation signals to B cells during T cell-B cell collaboration.
细胞间黏附分子1（ICAM-1，CD54）与白细胞功能相关抗原1（LFA-1，CD11a/CD18）之间的相互作用在T细胞与B细胞协作中起关键作用。开展当前实验以确定在T细胞与B细胞协作过程中，这些黏附分子在人外周血T细胞和B细胞上的表达及分布情况。静息CD4⁺ T细胞大多为ICAM-1阴性，而固定化抗CD3单克隆抗体（mAb）可迅速诱导ICAM-1表达。相比之下，大多数B细胞在激活前就表达ICAM-1，且随着刺激其密度进一步增加。B细胞和CD4⁺ T细胞在激活前均表达LFA-1，不过CD4⁺ T细胞上的密度要大得多。开发了一种用于电子显微镜分析的双重染色方法，可在T细胞与B细胞协作过程中评估ICAM-1的表达及分布情况。在所检测的实验条件下，B细胞显示ICAM-1呈均匀分布。相反，ICAM-1在CD4⁺ T细胞表面具有高度流动性。如果T细胞不固定，即使在4℃染色，也会导致ICAM-1迅速重新分布形成聚集体。然而，通过在染色程序前固定细胞，可准确评估ICAM-1在CD4⁺ T细胞上的分布情况。大多数（85%）固定的活化CD4⁺ T细胞显示ICAM-1呈均匀分布。然而，当活化的CD4⁺ T细胞与B细胞共培养时，ICAM-1在CD4⁺ T细胞而非B细胞上发生重新分布，使得大多数（85%）位于与B细胞附着点处或紧邻该附着点。未发现LFA-1在T细胞或B细胞上有重新分布。这些发现表明，激活的T细胞上ICAM-1表达密度的快速变化以及ICAM-1的流动性可能在T细胞与B细胞协作过程中为B细胞提供激活信号方面发挥作用。
