Recognition of the Self Idiotype by T Cells
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To investigate the initial stages of recognition of the self idiotype (Id) by T cells, we examined the early increase in cytoplasmic free calcium ([Ca<sup>2+</sup>]i) occurring in murine CD4<sup>+</sup> T cells specific for a model Id, Id315, following their interaction with the Id. The changes in [Ca<sup>2+</sup>]i were monitored with stopped-flow fluorometry by loading T cells with fura 2, a Ca<sup>2+</sup>-binding fluorescent dye. An increase of [Ca<sup>2+</sup>]i in the Id-specific T cell line was dependent on the presence of both antigen-presenting cells (APC) and Id315. When T cells were mixed with APC pulsed with M315 for 90min at 37C, a significant increase in T cell [Ca<sup>2+</sup>]i was observed within one second. A pronounced elevation in [Ca<sup>2+</sup>]i was also observed in T cells after their interaction with APC which had been pulsed for 90min with V<sub>L</sub>-315 Id-containing proteins (such as V<sub>L</sub>-315, L<sup>315</sup>, Fv-315 or Fab'-315 fragments). In contrast, pulsing APC for 5min with the V<sub>L</sub> fragment produced little or no change in the [Ca<sup>2+</sup>]i. These results suggest that V<sub>L</sub> must be further processed by APC before it can be recognized by T cells. Indeed, a synthetic V<sub>L</sub> region peptide (positions 91-108, designated as P18) produced an elevation in T cell [Ca<sup>2+</sup>]i when mixed with APC without pulsing.
- MICROBIOLOGY and IMMUNOLOGY
MICROBIOLOGY and IMMUNOLOGY 36(4), 407-418, 1992
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