The unsupervised hierarchical clustering distinguished two main clusters of traits ( Figure 3 ). The first cluster of 14 traits (Cluster A) could be divided into two groups: i) a group of four traits including one innate immunity cytokine (IFNA), two antibody levels (total IgG and specific IgG-Mh), and one FACScharacterized leukocyte subpopulation (CD16 + CD172A -) and ii) a group of 10 traits with nine hemogram-based cell counts or FACScharacterized leukocyte subpopulations (WBC, LYM, MON, NEU, EOS, CD16 + MHCII + , CD16 + CD2 + , CD4 -CD8 + cells) and two cell activity traits (IgM and IL10-PMAIONO). The second cluster of 18 traits (Cluster B) is also subdivided into two groups of traits: i) a group of three different cell response traits (IL6, IgA and IFNG-PMAIONO) and one FACS-characterized leukocyte subpopulation (IgM + cells), and ii) a group of nine cell response traits (IL12, IL4-PMAIONO, IL2-PMAIONO, TNF, PROLIF-PMA, HAPT, CRP, IL1B, IL8 and PHAG) and four FACS-characterized leukocyte subpopulations (CD4 + CD8 -, CD4 + CD8 -, TCRcd + and MHCII + CD172A + cells). In cluster A, the first group of 10 traits showed moderately to highly positive genetic correlations with each other. Indeed, r ĝ values greater than 0.4 were estimated between WBC, LYM, MON, NEU, EOS, CD4 -CD8 + and CD16 + CD2 + (NK) cells ( Figure 3 , Table S2 ). In cluster B, r ĝ values greater than 0.4 were estimated between i) TNF, IL8 and PHAG, and ii) CRP and HAPT ( Figure 3 , Table S2 ). Strong negative r ĝ values (,20.4) were found between a few traits from both clusters: i) TNF and three cell number traits (WBC, LYM, MON), ii) IL6 and CD16 + MHCII + , and iii) CRP and IgA.