Table 1.

CD4⁺ T-helper cell subsets in diseases.

	Autoimmunity	Cancer	Bacterial infection	Viral infection
Treg	Prevent immunopathology†	Suppress tumor immunity‡	Suppress host defense‡	Can suppress immunopathology† Suppress CTL responses, promoting viral replication‡
Th17	Cause immunopathology‡	Can promote tumor clearance† Can promote angiogenesis‡	Promote bacterial clearance†	May prevent secondary complications† Cause immunopathology and can inhibit CTL responses enhancing viral replication‡
Th1	Cause organ-specific autoimmunity‡	Promote CTL killing of tumor†	Clearance of intracellular infections†	Promote CTL killing of infected cells†
Th2/antibody	Cause systemic autoimmunity‡ Suppress Th1 autoimmunity†	Can be used to clear some cancers†	Clearance of extracellular infections†	Help neutralizing antibody production†

^†Protective role.

^‡Detrimental role.

CTL: Cytotoxic T lymphocyte.