In comparison to wild-type mice, GR9 fibrosarcoma-bearing mice exhibited a strong decrease in several immune cell subpopulations, with a significant reduction (p < 0.05) in TCD3+ (18.0 vs. 33.1%), TCD8+ (3.4 vs. 6.9%), and TCD4+ (14.6 vs. 26.1%) lymphocytes; moreover, a significant increase in Treg cells was found (10.6 vs. 4.4% of CD4+ cells) (Table 1). Here, CD4 is linked to fibrosarcoma.