CD4 lymphocytes also decreased in number after the infection with the ΔSPI1 mutant, i.e. another mutant in which, similarly to the SPI2o mutant, SPI-1 was absent while SPI-2 was present, although in this case the decrease did not reach statistical significance (P = 0.0634, see also Table 2). The gene discussed is SPI1; the disease is infection.