srd-28 Antibody

Definition and Target

Anti-CD28 antibodies are immunoglobulins targeting CD28, a co-stimulatory receptor on T cells critical for adaptive immune activation. These antibodies modulate T cell responses by either agonizing or antagonizing CD28 signaling pathways .

Key Features of CD28:

• Binds ligands CD80/CD86 on antigen-presenting cells (APCs) .

• Delivers a "second signal" for T cell activation alongside TCR engagement .

• Downregulated in chronic immune activation (e.g., autoimmune diseases, transplant rejection) .

Antagonist Antibodies

• Monovalent Binding: Prevents CD28 multimerization, blocking co-stimulation. Example: MF280 (VH/VL-Fc heterodimer) reduces IL-2 secretion by 70% in Jurkat T cells .

• Receptor Occupancy: EC₅₀ values for inhibition range from 35–53 ng/mL .

• Immune Evasion: Humanized variants (e.g., hCD28.3) minimize immunogenicity while retaining binding affinity (K_D ~1–10 nM) .

Agonist Antibodies

• Divalent Formats: Enhance T cell proliferation and cytokine production (e.g., IL-2, IFN-γ) .

• Fc-Dependent Effects: IgG1 Fc domains amplify agonism via FcγR interactions .

Autoimmune Diseases

• Efficacy: Anti-CD28 antagonists reduce T cell activation in models of transplant rejection (60–80% graft survival improvement) .

• Clinical Correlation: CD28 downregulation on CD4+ T cells correlates with poor outcomes in idiopathic pulmonary fibrosis (IPF) .

Infectious Diseases

• HIV Resistance: Anti-CD28 costimulation via beads reduces CCR5 expression and HIV p24 production by >90% .

Oncology

• Plasma Cell Survival: CD28 signaling sustains long-lived plasma cells (LLPCs) via B lymphocyte–induced maturation protein-1 (BLIMP-1) regulation .

Key Studies on Anti-CD28 Antibodies

Future Directions

• Bispecific Antibodies: Combining CD28 antagonists with checkpoint inhibitors (e.g., CTLA-4) .

• Gene Editing: CRISPR-based CD28 modulation in CAR-T therapies .