FasL and the NKG2D receptor are required for the secretion of the Tag7/PGRP‐S–Hsp70 complex by the cytotoxic CD8⁺ lymphocytes

Abstract

SummaryTag7 (PGRP-S or PGLYRP1), while possessing an antimicrobial activity, also exhibits an antitumor effect when in complex with the major heat shock protein Hsp70. The cytotoxic Tag7-Hsp70 complex is secreted by lymphocytes after interaction with the HLA-negative tumors. Previously, we have shown that IL-2 induces formation of the CD4 1 and CD8 1 cytotoxic subpopulations of human lymphocytes, which kill tumor cells through the FasL-Fas interaction. Here, we show that only the CD8 1 T cells are able to secrete the Tag7-Hsp70 complex. For its secretion the same proteins on the surface of the lymphocytes and target cells, which are involved in the contact lysis, are necessary as well. The interaction of Fas receptor with FasL leads to an activation of the Tag7-Hsp70 complex in the lymphocyte membrane fraction, and here FasL acts as a receptor that induces intracellular signaling in lymphocytes. An interaction of the MicA stress ligand with the NKG2D receptor is necessary for the release of this cytotoxic complex. It is possible, that CD8 1 T lymphocytes interacting with a target cell can both carry out the contact killing of these cells and to secrete the cytotoxic factor.

Tilorone activates NK cells and cytotoxic lymphocytes that kill HLA‐negative tumor cells

“…As shown in our previously, lymphocytes activated by IL‐2 or Tag7 can kill tumor cells by contact lysis, which is mediated through the FasL–Fas interaction, or by secretory lysis, releasing the soluble Tag7–Hsp70 cytotoxic complex interacting with the TNFR1 receptor. However, a prerequisite for the secretion of this complex is the formation of the contact zone between activated lymphocyte and tumor cell due to the FasL–Fas interaction .…”

Tag7 (PGLYRP1) Can Induce an Emergence of the CD3+CD4+CD25+CD127+ Cells with Antitumor Activity

“…Results of cell sorting were always verified by flow cytometry, and there were no experiments with less than 80% purity. Specific antibodies to CD127 or Tag7 were coupled to magnetic beads coated with the anti-rabbit antibodies, following the methods of Sashchenko et al [ 25 ].…”

“…Polyclonal antibodies to the N-terminus of Fas (N-18) and C-terminus of FasL (С-178) were from Sigma (United States); CD4-PE, CD4-FITC, CD4-TC, CD25-FITC, CD127-PE, FasL-FITC, FasL-PE, and Fas-PE were from Caltag Medsystems (Buckingham, UK). Control antibodies were IgG from rabbit serum (Sigma-Aldrich, St. Louis, MO), following the methods of Sashchenko et al [ 25 ].…”

Mechanisms of Action of the PGLYRP1/Tag7 Protein in Innate and Acquired Immunity

“…Это, вопервых, индукция цитотоксического сигнала с последующей гибелью опухолевых клеток-мишеней благодаря связыванию FasL лимфоцита с рецептором Fas опухолевой клетки. Во-вторых, секреция в зону контакта клеток растворимого цитотоксического комплекса Tag7-Hsp70 [52]. Предполагается, что связывание рецептора Fas с FasL на поверхности лимфоцита индуцирует накопление комплекса Tag7-Hsp70 во внутриклеточных мембранах лимфоцитов.…”

“…Предполагается, что связывание рецептора Fas с FasL на поверхности лимфоцита индуцирует накопление комплекса Tag7-Hsp70 во внутриклеточных мембранах лимфоцитов. Для секреции этого комплекса необходимо дополнительное связывание MicA на поверхности клетки-мишени с NKG2D на поверхности лимфоцита, предположительно для создания межклеточной контактной зоны [52] [54]. В присутствии Hsp70 в высокой концентрации Tag7-HspBP1 диссоциирует с образованием цитотоксического комплекса Tag7-Hsp70 [53].…”