Human Anti-Human Lck monoclonal Antibody, clone SFB784 [PE]

SEC2, a major histocompatibility complex class II (MHC II)-dependent T-cell mitogen, binds MHC II and T-cell receptor (TCR) Vs to induce effective co-stimulating signals for clonal T-cell expansion. We previously characterized a SEC2 mutant with increased recognition of TCR Vs, ST-4, which could intensify NF-B signaling transduction, leading to IL-2 production and T-cell activation. In this study, we found that in contrast to SEC2, ST-4 could induce murine CD4(+) T-cell proliferation in a V8.2- and V8.3-specific manner in the absence of MHC II+ antigen-presenting cells (APCs). Furthermore, although IL-2 secretion in response to either SEC2 or ST-4 stimulation was accompanied by up-regulation of protein kinase C (PKC), inhibitor of B (IB), and IB kinase (IKK/), IB, and NF-B in mouse splenocytes, only ST-4 could activate CD4(+) T cells in the absence of MHC II+ APCs through the PKC/NF-B signaling pathway. The PKC inhibitor AEB071 significantly suppressed SEC2/ST-4-induced T-cell proliferation, CD69 and CD25 expression, and IL-2 secretion with or without MHC II+ APCs. Further, SEC2/ST-4-induced changes in PKC/NF-B signaling were significantly relieved by AEB071 in a dose-dependent manner. Using Lck siRNA, we found that Lck controlled SEC2/ST-4-induced phosphorylation of PKC. We also demonstrated that the IL-2R/STAT5 pathway is essential for SEC2/ST-4-induced T-cell activation. Collectively, our data demonstrate that an enhanced ST-4-TCR interaction can compensate for lack of MHC II and stimulate MHC II-free CD4(+) T-cell proliferation via PKC/NF-B and IL-2R/STAT5 signaling pathways. Compared with SEC2, intensified PKC/NF-B and IL-2R/STAT5 signals induced by ST-4 lead to enhanced T-cell activation. The results of this study will facilitate better understanding of TCR-based immunotherapies for cancer.

Primary immunodeficiencies (PIDs) form a large and heterogeneous group of mainly rare disorders that affect the immune system. T-cell deficiencies account for about one-tenth of PIDs, most of them being monogenic. Apart from genetic and clinical information, lots of other data are available for PID proteins and genes, including functions and interactions. Thus, it is possible to perform systems biology studies on the effects of PIDs on T-cell physiology and response. To achieve this, we reconstructed a T-cell network model based on literature mining and TPPIN, a previously published core T-cell network, and performed semi-quantitative dynamic network simulations on both normal and T-cell PID failure modes. The results for several loss-of-function PID simulations correspond to results of previously reported molecular studies. The simulations for TCR PTPRC, LCK, ZAP70 and ITK indicate profound changes to numerous proteins in the network. Significant effects were observed also in the BCL10, CARD11, MALT1, NEMO, IKKB and MAP3K14 simulations. No major effects were observed for PIDs that are caused by constitutively active proteins. The T-cell model facilitates the understanding of the underlying dynamics of PID disease processes. The approach confirms previous knowledge about T-cell signaling network and indicates several new important proteins that may be of interest when developing novel diagnosis and therapies to treat immunological defects.