B2M and mastitis: Multivariate mixed models, taking into account the clustering of left and right breast milk samples of a woman and adjusted on infant age at sampling, confirmed the association between HIV infection and MIG, IP-10, IL-1RA and CRP, as well as B2M and sCD14 (see Additional file 2: Table S2 for multivariate mixed models assessing the effect of HIV infection on breast milk immune factors, on samples without sub-clinical mastitis).