Zeta ICOS (CD278) Antibody. Zeta’s rabbit recombinant antibody recognizes ICOS (inducible T-cell Co-Stimulator or CD278), a member of the CD28/CTLA-4 superfamily that regulates T cell activity and immune responses. ICOS is primarily expressed on activated CD4+ and CD8+ T cells where it regulates immune responses and plays a role in the regulation of T-follicular helper cells. The ICOS protein contains an extracellular IgV-like domain, a transmembrane domain, and an intracellular domain with a YMFM motif. Upon binding to its ligand, ICOS potentiates the T cell response to antigen through activation of the PI3K signaling pathway. ICOS is a sensitive marker for identifying T-cell lymphomas of follicular helper T-cell origin, especially certain patterns of angioimmunoblastic T-cell lymphoma (AITL) and peripheral T-cell lymphomas with T-follicular helper phenotype (PTCL-TFH).
ICOS acts as a co-stimulatory molecule in the CD28/CTLA-4 family where it is expressed primarily on activated T cells (both CD4⁺ and CD8⁺), playing a role in T-cell proliferation, cytokine production, and survival by binding to ICOS ligand (ICOS-L) on antigen-presenting cells, modulating immune responses.
Increasingly, ICOS is being used to examine tumor microenvironments to identify activated T cells infiltrating tumors immune activation status and to quantify immune activation status in tumor-infiltrating lymphocytes (TILs). ICOS has prognostic potential where high ICOS⁺ T-cell infiltration in certain tumors (e.g., melanoma, gastric cancer) may correlate with better prognosis or immunotherapy responsiveness.
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