CD4 and lymphoma: It has been observed that tumor-bearing mice with high C5a-producing lymphoma cells had significantly accelerated tumor progression with decreased CD4+ and CD8+ T cells in the tumor, whereas mice with low C5a-producing lymphoma cells had a significantly reduced tumor burden with increased IFN-γ-producing CD4+ and CD8+ T cells in the spleen and tumor-draining lymph nodes [21].