CD4 and ataxia telangiectasia: In adaptive immunity, leptin exerts pro-inflammatory effects in AT through enhancing the proliferation of B and CD4+ T lymphocytes toward producing pro-inflammatory cytokines and reducing the production of anti-inflammatory Th2 cytokines [196].It is, therefore, suggested that B. fragilis may exert anti-inflammatory effects on AT in infants, due to their ability to modulate immune cell function and ameliorate AT inflammation.