The transient decrease in lymphocyte subsets reflected the decrease in absolute lymphocyte counts observed in all cats after FCV Challenge I [28]; this might represent again the cell migration from blood to the regional lymph nodes as discussed for FCV Vaccination I. However, the extent of the decrease was much greater after FCV Challenge I compared to FCV Vaccination I. At day 6 after the experimental FCV infection, the vaccinated cats had significantly higher CD5+ lymphocytes and CD8+ lymphocytes. The gene discussed is CD5; the disease is infection.