Which cell surface marker is defective in autoimmune lymphoproliferative syndrome (ALPS) leading to apoptosis?

In autoimmune lymphoproliferative syndrome (ALPS), the defect is primarily associated with the CD95 receptor, also known as Fas. CD95 is critical in the process of apoptosis, which is the programmed cell death essential for maintaining immune homeostasis by eliminating activated and potentially autoreactive lymphocytes. In individuals with ALPS, mutations or defects in the CD95 pathway result in impaired apoptosis, leading to the accumulation of lymphocytes and an increased risk of autoimmune disorders due to the failure to effectively remove auto-reactive cells.

The role of CD95 in apoptosis highlights its importance in regulating immune responses and preventing autoimmunity. When the signaling through CD95 is disrupted, either through genetic mutations or other forms of dysfunction, it leads to the symptoms associated with ALPS, such as lymphadenopathy and splenomegaly due to excessive lymphocyte proliferation.

Other options represent different markers involved in immune function but do not specifically relate to the apoptotic pathway affected in ALPS. Understanding the unique role of CD95 in apoptosis underlines its significance in the context of this syndrome.