Compared with the uninfected tilapia (Fig 3A and 3B), nondepleted fish infected with E. piscicida showed a marked expansion of CD4-1+ T cells on 5 DPI (Fig 3I middle panel and 3J), but infected fish with CD4-1+ T-cell depletion exhibited a significant defect in CD4-1+ T-cell expansion during bacterial infection (Fig 3I and 3J). The gene discussed is ITGA2B; the disease is bacterial infectious disease.