期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：15
页码：8471-8476
DOI：10.1073/pnas.96.15.8471
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Contact with antigen-presenting cells (APCs) initiates an activation cascade within T lymphocytes, including a rise in cytosolic calcium, lymphokine production, and cell division. Although T cell-APC physical contact is required for an immune response, little is known about the patterns of cellular interactions and their relation to activation. Calcium imaging combined with an optical trap enabled the T cell contact requirements and polarity to be investigated at the single-cell level. APCs or anti-CD3 mAb-coated beads were trapped with a laser and placed at different locations along the T cell, which has a polarized appearance defined by the shape and direction of crawling. T cells were 3-fold more sensitive to APC contact made at the leading edge of the T cell than with contact made at the tail. Anti-CD3 mAb-coated 6-{micro}m beads induced calcium signaling with {approx}10-fold higher frequency and {approx}4-fold shorter latency on contact with the leading edge of the T cell than on contact with the trailing edge. Alterations in antibody density (2 to 500 per {micro}m2) and bead size (1 to 6 {micro}m in diameter) were used to determine the spatial requirements and the minimal number of receptors which must be engaged to transmit a positive signal. T cell response percentage, latency, and calcium-signaling pattern (transient vs. sustained or oscillatory) depended on antibody density on the bead. The presence of {approx}170 anti-CD3 mAb within the contact area elicited a detectable T cell calcium response. We propose here that engagement of no more than 340 T cell receptors ({approx}1% of the total on the cell) is sufficient to initiate Ca2+ signaling. The minimal contact area was {approx}3 {micro}m2.
