While insufficient cell death of activated T cells can result in autoimmune disorders, elimination of too many T cells can lead to immunodeficiency. Therefore, T lymphocyte fate is highly regulated and requires that cells can switch from an apoptosis-resistant towards an apoptosis-sensitive state. This switch is tightly controlled by various effector molecules. Basically, two separate pathways control the fate of antigen-activated T cells: activation-induced cell death (AICD) and activated T cell autonomous death (ACAD). Autoreactive T lymphocytes are eliminated by restimulation via their T cell receptor (TCR) and undergo AICD involving death receptors (extrinsic pathway). In contrast, ACAD can lead to T cell deletion without TCR restimulation, and is determined by the ratio between anti-and pro-apoptotic Bcl-2 family members at the mitochondria (intrinsic pathway). While the extrinsic and the intrinsic pathway lead to caspase activation, non-caspase proteases (e.g., cathepsins) can be released by the lysosomes and might contribute to AICD as well as to ACAD. Activated T cells posses cell death escape mechanisms which are needed for survival of (memory) T cells, but are deleterious for autoimmune disorders or progression of T cell lymphomas.

Life and death of peripheral lymphocytes is strictly controlled to maintain physiologic levels of T and B cells. Activation-induced cell death (AICD) is one mechanism to delete superfluous lymphocytes by restimulation of their immunoreceptors and it depends partially on the CD95/CD95L system. Recently, we have shown that hematopoietic progenitor kinase 1 (HPK1) determines T-cell fate. While full-length HPK1 is essential for NF-κB activation in T cells, the C-terminal fragment of HPK1, HPK1-C, suppresses NF-κB and sensitizes toward AICD by a yet undefined cell death pathway. Here we show that upon IL-2–driven expansion of primary T cells, HPK1 is converted to HPK1-C by a caspase-3 activity below the threshold of apoptosis induction. HPK1-C se-lectively blocks induction of NF-κB–dependent antiapoptotic Bcl-2 family members but not of the proapoptotic Bcl-2 family member Bim. Interestingly, T and B lymphocytes from HPK1-C transgenic mice undergo AICD independently of the CD95/CD95L system but involving caspase-9. Knock down of HPK1/HPK1-C or Bim by small interfering RNA shows that CD95L-dependent and HPK1/HPK1-C–dependent cell death pathways complement each other in AICD of primary T cells. Our results define HPK1-C as a suppressor of antiapoptotic Bcl-2 proteins and provide a molecular basis for our understanding of CD95L-independent AICD of lymphocytes.

Background: In contrast to psychological interventions the usefulness of acupuncture as an adjuvant therapy in rheumatoid arthritis (RA) has not yet been demonstrated. Objective: The efficacy of auricular electroacupuncture (EA) was directly compared with autogenic training (AT). Methods: Patients with RA (n = 44) were randomized into EA or AT groups. EA and lessons in AT were performed once weekly for 6 weeks. Primary outcome measures were the mean weekly pain intensity and the disease activity score 28 (DAS 28); secondary outcome measures were the use of pain medication, the pain disability index (PDI), the clinical global impression (CGI) and pro-inflammatory cytokine levels, which were assessed during the study period and 3 months after the end of treatment. Results: At the end of the treatment and at 3-month follow-up a clinically meaningful and statistically significant improvement (p < 0.05) could be observed in all outcome parameters and both groups. In contrast to the AT group, the onset of these effects in the EA group could already be observed after the 2nd treatment week. In the 4th treatment week the EA group reported significantly less pain than the AT group (p = 0.040). After the end of treatment (7th week) the EA group assessed their outcome as significantly more improved than the AT group (p = 0.035). The erythrocyte sedimentation rate in the EA group was significantly reduced (p = 0.010), and the serum concentration of tumor necrosis factor-alpha was significantly increased compared to the AT group (p = 0.020). Conclusions: The adjuvant use of both EA and AT in the treatment of RA resulted in significant short- and long-term treatment effects. The treatment effects of auricular EA were more pronounced.