Dennehy Kevin M, Kerstan Andreas, Bischof Astrid, Park Jung-Hyun, Na Shin-Young, Hünig Thomas
Institute for Virology and Immunobiology, University of Würzburg, 97078 Würzburg, Germany.
Int Immunol. 2003 May;15(5):655-63. doi: 10.1093/intimm/dxg063.
Mitogenic anti-CD28 antibody stimulates all peripheral T cells to proliferate in the absence of TCR ligation, providing an exception to the two-signal requirement of T cell responses. This antibody preferentially recognizes a mobilized signaling-competent form of CD28, normally induced following TCR ligation, thus providing a unique non-physiological tool to dissect CD28-specific signals leading to T cell proliferation. The protein kinase C (PKC)theta-NF-kappaB pathway has recently been shown to integrate TCR- and CD28-derived signals in co-stimulation. We now demonstrate that this pathway is activated by mitogenic anti-CD28 antibody stimulation. In contrast to conventional anti-CD28 antibody, mitogenic anti-CD28 antibody induced activation of phospholipase Cgamma and Ca(2+) flux in peripheral rat T cells despite no or low levels of inducible tyrosine phosphorylation of TCRzeta chain, TCRzeta-associated protein of 70 kDa (ZAP-70) or linker for activation of T cells (LAT)-critical components of the TCR signaling machinery. Nevertheless, PKCtheta kinase activity in vitro was increased following mitogenic anti-CD28 antibody stimulation, as was membrane association of both PKCtheta and Bcl10. As downstream targets of PKCtheta activation, NF-kappaB components translocated to the nucleus at levels comparable to those after TCR-CD28 co-stimulation. NF-kappaB translocation was diminished by PKCtheta inhibition, as was induction of the NF-kappaB/AP-1 responsive activation marker CD69. We propose that co-stimulation is a sequential process in which appropriate TCR engagement is required to mobilize CD28 into a signaling-competent form which then activates the PKCtheta-NF-kappaB pathway necessary for IL-2 production and proliferation.
促有丝分裂抗CD28抗体可刺激所有外周T细胞在无TCR连接的情况下增殖，这是T细胞反应双信号要求的一个例外。该抗体优先识别一种通常在TCR连接后诱导产生的、具有信号传导能力的可动员形式的CD28，从而提供了一种独特的非生理性工具来剖析导致T细胞增殖的CD28特异性信号。蛋白激酶C（PKC）θ-NF-κB途径最近已被证明在共刺激中整合了TCR和CD28衍生的信号。我们现在证明该途径可被促有丝分裂抗CD28抗体刺激激活。与传统抗CD28抗体不同，促有丝分裂抗CD28抗体可诱导外周大鼠T细胞中磷脂酶Cγ的激活和Ca(2+)通量，尽管TCRζ链、70 kDa的TCRζ相关蛋白（ZAP-70）或T细胞激活连接蛋白（LAT）（TCR信号传导机制的关键成分）的诱导型酪氨酸磷酸化水平很低或没有。然而，促有丝分裂抗CD28抗体刺激后，体外PKCθ激酶活性增加，PKCθ和Bcl10的膜结合也增加。作为PKCθ激活的下游靶点，NF-κB成分转位至细胞核的水平与TCR-CD28共刺激后的水平相当。PKCθ抑制可减少NF-κB转位，NF-κB/AP-1反应性激活标志物CD69的诱导也减少。我们提出，共刺激是一个连续的过程，其中需要适当的TCR结合来将CD28动员成一种具有信号传导能力的形式，然后激活IL-2产生和增殖所需的PKCθ-NF-κB途径。
