To examine whether Long COVID, and its accompanying affective symptoms and CFS are associated with immunoglobulin (Ig)A/IgM/IgG directed at neuronal proteins including myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), synapsin, α + β-tubulin, neurofilament protein (NFP), cerebellar protein-2 (CP2), and the blood–brain-barrier-brain-damage (BBD) proteins claudin-5 and S100B. Here, CD40LG is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.