Table 1.

Summary of evidence on Th cell subsets and chemokines in elderly asthma

Th cell subset	Key cytokines	Associated chemokines	Role in elderly asthma
Th1	IFN-γ, IL-2, TNF-α	CCL2, CXCL9, CXCL10	Promotes pro-inflammatory responses, associated with neutrophilic inflammation. Often implicated in severe, steroid-resistant asthma in elderly patients.
Th2	IL-4, IL-5, IL-13	CCL11, CCL17, CCL22	Drives eosinophilic inflammation, mucus production, and airway remodeling. A prominent feature in mild to moderate asthma in the elderly.
Th17	IL-17A, IL-22	CXCL8 (IL-8), CCL20	Enhances neutrophilic inflammation and airway remodeling. Linked to severe asthma and glucocorticoid resistance, particularly in older adults.
Treg	TGF-β, IL-10	CCL18, CX3CL1	Regulates immune tolerance and suppresses excessive inflammation. Decline in function is associated with increased asthma severity in the elderly.

Abbreviations: Th1: T helper 1 cells; Th2: T helper 2 cells; Th17: T helper 17 cells; Treg: Regulatory T cells; IFN-γ: Interferon gamma; TNF-α: Tumor necrosis factor alpha; TGF-β: Transforming growth factor beta; CCL2: C-C motif chemokine ligand 2; CXCL9: C-X-C motif chemokine ligand 9; CXCL10: C-X-C motif chemokine ligand 10; CCL11: C-C motif chemokine ligand 11; CCL17: C-C motif chemokine ligand 17; CCL22: C-C motif chemokine ligand 22; CXCL8: C-X-C motif chemokine ligand 8; CCL20: C-C motif chemokine ligand 20; CCL18: C-C motif chemokine ligand 18; CX3CL1: C-X3-C motif chemokine ligand 1.