How Antibodies and Cytokines Coordinate Antiviral Immunity
Antibodies: Precision Targeting of Viruses
Antibodies (immunoglobulins) are Y-shaped proteins secreted by differentiated B cells (plasma cells). Each antibody's variable region binds a specific viral epitope (antigenic determinant).
Key Antibody Functions
- Neutralization: Blocks viral attachment/entry by occupying receptor-binding sites (e.g., anti-spike IgG for SARS-CoV-2).
- Opsonization: Fc region tags virus for phagocytosis by macrophages/neutrophils.
- Complement activation: Classical pathway → lysis of enveloped viruses, enhanced opsonization, inflammation.
- Antibody-dependent cellular cytotoxicity (ADCC): NK cells recognize Fc-bound infected cells → lysis.
- Mucosal immunity: Secretory IgA (sIgA) at respiratory/GI mucosa prevents viral adhesion.
Cytokines: The Immune System's Communication Network
Cytokines are soluble signaling proteins (<5–20 kDa) produced by immune and non-immune cells. They act in autocrine, paracrine, and endocrine fashions.
Major Antiviral Cytokine Families
| Family | Key Members | Primary Antiviral Roles |
|---|---|---|
| Type I Interferons | IFN-α (13 subtypes), IFN-β, IFN-ε, IFN-κ, IFN-ω | Induce antiviral state in neighboring cells (ISGs: PKR, OAS/RNase L, Mx proteins); enhance MHC-I presentation; activate NK cells, DCs; bridge innate/adaptive |
| Type II Interferon | IFN-γ (NK, CD4⁺ Th1, CD8⁺ T) | Macrophage activation; Th1 polarization; MHC upregulation; antiviral synergy with Type I IFNs |
| Type III Interferons | IFN-λ1/2/3 (IL-29/28A/28B) | Mucosal antiviral defense (epithelial receptors); less systemic inflammation |
| Proinflammatory | TNF-α, IL-1β, IL-6, IL-12, IL-18 | Fever, acute phase, leukocyte recruitment, Th1/CTL differentiation |
| Chemokines | CXCL9/10/11 (IP-10, MIG, I-TAC), CCL2/3/4/5 | Recruit T cells, NK cells, monocytes to infection site |
| Regulatory | IL-10, TGF-β, IL-35 | Limit immunopathology; balance clearance vs. tissue damage |