Underexpression and overexpression of Fas and Fas ligand: a double-edged sword.

OBJECTIVE

To compare autoimmune lymphoproliferative syndrome (ALPS) and Stevens-Johnson syndrome (SJS) with respect to the defects in Fas- and Fas ligand (FasL)-mediated apoptosis.

DATA SOURCES: Selected reviews, case reports, and original studies were searched in PubMed and MEDLINE for the keywords ALPS, SJS, Fas, FasL, and apoptosis.

STUDY SELECTION: Case reports of ALPS and SJS were selected as examples of Fas- and FasL-mediated diseases. In addition, we selected articles that examined the pathophysiology of apoptosis in the context of Fas-FasL interaction.

RESULTS

Failure to initiate apoptosis of abnormal T lymphocytes occurs in such diseases as ALPS, leading to the accumulation of double negative T cells with an increase in autoimmunity. In contrast to apoptotic failure, SJS is associated with a pathological increase in programmed keratinocyte cell death.

CONCLUSION

The consequences of dysregulated Fas- and FasL-mediated apoptosis leads to self-reactivity, malignant transformation, and immune dysfunction. An understanding of underlying mechanisms and qualitative assessment of Fas and FasL may have clinical benefits when control of these homeostatic mechanisms is in question.