In the field of acute pyelonephritis expression of HLA-DR on monocytes, the rate of apoptosis of monocytes and the rate of apoptosis of NKT cells decrease; in CAP absolute counts of NK cells, CD4-lymphocytes, CD8-lymphocytes and B-lymphocytes decrease; in intraabdominal infections absolute counts of CD8-lymphocytes and the rate of apoptosis of CD8-lymphocytes decrease; in primary bacteremia the rate of apoptosis of NKT cells increase; and in VAP/HAP the rate of apoptosis of NKT cells and of NK cells increase. The gene discussed is CD4; the disease is ventilator-associated pneumonia.