Debebe et al. showed that similarities in regions of the MHC molecule that interact with different immune cell receptors can be thought of in terms of different 'spaces' (which are defined by an axis for each type of receptor). They found that MHCs that are similar in the T-cell receptor (TCR) axis are associated with disease outcomes for HLTV-1, hepatitis C virus (HCV) and HIV-1. Disease outcomes for HIV-1 are also associated with MHCs that show similarity in the killer immunoglobulin-like receptor (KIR) axis. For the diseases tested, no MHCs were found to be similar in the region that interacts with the leukocyte immunoglobulin-like receptor (LILR) carried by myeloid cells (MC). CD8: CD8+ T cells; NK: natural killer cells; blue circle: peptide.