Fig. 3

C3 deposition in GC tissues was associated with systemic Complement depletion. Regional deposition of C3 in GC tissues can be evaluated by the intensity of IHC staining (a), with score 0–3 for negative, weak, moderate and strong staining respectively. The average score of C3 deposition was calculated by five independent high-power fields of IHC section from each patient. The average score in primary GC tissues was much higher than that in adjacent normal tissues (b, left panel). Additionally, the case distribution based on C3 score presented as low (n = 41) and high C3 deposition (n = 35 as high and n = 30 as severe) in GC tissues (b right panel). The filling colors were black, brown and red for low, high and severe IHC scores, respectively. Linear relationship between average IHC C3 score and plasma levels of C3 and C4 at baseline and surgery was investigated (c). The relationship between IHC score and intraoperative plasma levels of C3a (P < 0.001), fB (P < 0.001) and C5a (P = 0.444) was explored using ELISA method (d, n = 30). The mRNA expression of C3 in GC tissues and C5 in the peripheral blood were extracted from TCGA database to assess their relationship, with no correlation found (e; P = 0.137, n = 384)