The exact cause of pars planitis remains unknown (see Table 2), but CD4+ T cells that express an activation marker CD69 (an early activation marker) in either peripheral blood (Murphy et al. 2004) or in the aqueous humor are found, respectively, in patients with pars planitis and with idiopathic uveitis (Calder et al. 1999). The gene discussed is CD69; the disease is pars planitis.