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     Western blot analysis using SOD1 mouse mAb against Hela (1), NIH/3T3 (2), A549 (3) and A431 (4) cell lysate.    

  
  

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     Confocal Immunofluorescence analysis of PANC-1 (left) and SKBR-3 (right) cells using SOD1 mouse mAb (green). Red: Actin filaments have been labeled with DY-554 phalloidin. Blue: DRAQ5 fluorescent DNA dye.    

  
  

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     Confocal Immunofluorescence analysis of 3T3-L1 cells using SOD1 mouse mAb (green). Blue: DRAQ5 fluorescent DNA dye.    

  
  

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     Flow cytometric analysis of A431 cells using SOD1 mouse mAb (green) and negative control (purple).    

  
  

The inducible T-cell co-stimulator (ICOS), a member of the CD28 superfamily, is a transmembrane protein expressed on activated T cells. It binds to ICOS ligand (ICOSL, B7-H2) on antigen-presenting cells, delivering co-stimulatory signals critical for T-cell activation, differentiation, and survival. ICOS is particularly important in follicular helper T (Tfh) cell development and Th2-mediated immune responses. Dysregulation of the ICOS/ICOSL pathway is implicated in autoimmune diseases, cancer, and transplant rejection.

ICOS-targeting antibodies have emerged as therapeutic tools with dual potential. Antagonistic antibodies block ICOS signaling to suppress pathogenic T-cell activity in autoimmune conditions like lupus and rheumatoid arthritis. Conversely, agonistic antibodies enhance ICOS-mediated co-stimulation to boost anti-tumor immunity in oncology. For example, MEDI-570 (anti-ICOS) and vopratelimab (ICOS agonist) have been evaluated in clinical trials for cancers and autoimmune disorders.

The therapeutic effect of ICOS antibodies also depends on IgG subclass. IgG4-based antibodies often act as antagonists by blocking ligand binding, while IgG1 variants may promote receptor clustering or antibody-dependent cytotoxicity. Challenges include balancing efficacy with immune-related adverse events, given ICOS's broad role in adaptive immunity. Ongoing research focuses on optimizing antibody design and combination therapies to harness ICOS modulation for precision immunotherapy.