HLA-DRbeta 1 harbours the major MS susceptibility genes and when they looked for the genes associated with B cell immune responses to viral targets EBV they pulled out HLA-DRB1.
We have been teaching that CD8 responses are associated with anti-viral responses due to loading of viral peptides in the golgi apparatus and so if you see a CD8 T cell mediated response think . Virus. Likewise CD4 responses are restricted by MHC class II such as HLA-DR and the MHC is loaded in endosomes (CLICK HERE).
However it is not so clear cut and virus peptides can be loaded into MHC class II
Endogenous antigen processing drives the primary CD4(+) T cell response to influenza. Miller MA, Ganesan AP, Luckashenak N, Mendonca M, Eisenlohr LC. Nat Med. 2015;21(10):1216-22.By convention, CD4(+) T lymphocytes recognize foreign and self peptides derived from internalized antigens in combination with major histocompatibility complex class II molecules. Alternative pathways of epitope production have been identified, but their contributions to host defense have not been established. We show here in a mouse infection model that the CD4(+) T cell response to influenza, critical for durable protection from the virus, is driven principally by unconventional processing of antigen synthesized within the infected antigen-presenting cell, not by classical processing of endocytosed virions or material from infected cells. Investigation of the cellular components involved, including the H2-M molecular chaperone, the proteasome and γ-interferon-inducible lysosomal thiol reductase revealed considerable heterogeneity in the generation of individual epitopes, an arrangement that ensures peptide diversity and broad CD4(+) T cell engagement.