Project 1: Autoimmune Lymphoproliferative Syndrome is a disorder characterized by massive expansion of a CD4-/CD8- T cell population and autoimmunity similar to that in lpr mice. Recently, it has been shown that both ALPS patients and lpr mice have mutations of the FAS gene and Defective apoptosis. Here, we report on immune function in ALPS patients. In initial studies we showed that the circulating level of IL-10 was greatly elevated I all ALPS patients in rough proportion to their level of CD4-/CD8- T cells. In addition, while plasma levels of TNFalpha were increased 3 - 9 fold, levels of IL-1 and IL-6 were normal. I subsequent studies, we determined cytokine production (IL-4, IL-5 IFN-gamma, Il-2) in cultured ALPS T cell subpopulations stimulated with alphaCD3/alphaCD28 or alphaCD2/alphaCD28. We showed that ALPS patients CD4+/DR+ T cells produced increased amounts of IL-4 and IL-5 (10-30 fold, n=6) and decreased amounts of IFN-gamma (2-4 fold, n=6) as compared to CD4+/DR+ T cells of controls (n=4). In parallel studies, we showed that ALPS patient peripheral B (stimulated with SAC and IL-2) and T cells (stimulated as above) produced decreased amounts of IL-10 (3-10 fold) whereas patient peripheral monocytes (stimulated with LPS) produced increased amounts of IL-10 (5 fold, n=3) as compared to control cells. Finally, we determined that patient monocytes (stimulated with LPS/IFN-gamma) produces 30-fold less Il-12 than normal cells. In conclusion, ALPS is associated with the presence of DR+ T cells which respond upon stimulation with a Th2-type cytokine profile; this, plus the increased production of IL-10 defines a cytokine mileau heading to autoimmunity. Project 2: Lamina propria, (LP) T cells are partially anergic T cells that respond poorly to a proliferative stimulus delivered via the TCR/CD3 pathway, but retain considerable ability to respond to a stimulus delivered via the CD2 co-stimulatory or accessory pathway. In the present study, we showed first that unstimulated LP T cells, as compared to unstimulated peripheral blood (PB) T cells, exhibit an increased level of apoptosis which is further increased following CD2 pathway stimulation, but not following via TCR/CD3 pathway stimulation. These results are in contrast to those obtained with PB T cells where neither stimulation via TCR/CD3 nor CD2 pathways increased the level of apoptosis above low baseline levels. We next showed that IL-2 had a sparing effect of apoptosis of unstimulated LP T cells in that IL-2 decreased and anti-IL-2 increased apoptosis of these cells; in contrast, IL-2 had no effect of apoptosis of CD2-pathway-stimulated cells. Finally, we showed that the increased apoptosis of LP T cells induces by CD2-pathway stimulation is inhibited when the Fas Antigen is blocked by a non-stimulatory anti-Fas antibody. Thus, these studies suggest that LP T cells are characterized by an increased susceptibility to Fas-mediated apoptosis most due to a "downstream" change in the Fas signaling pathway.