HLA-C and infection: As shown in Figure 5, infected animals (16 weeks old) with circulating MHC-IIlow monocytes and MRC1L-B− cells with a normal MHC-II expression level (Figure 1D) on day 4 post infection produced lower titres of antibodies against NDV than uninfected chickens (16 weeks old), as evaluated on day 14 post vaccination (S/P ratio: 7.6 ± 1.3 vs 9.1 ± 0.76, p = 0.0379).