CD4 and Parkinson disease: Furthermore, α-syn overexpression models have reported increased MHC II expression (Subbarayan et al., 2020) and other animal models of PD reported that infiltrating CD4 + T cells were surrounded by MHC-II expressing microglia, supporting the notion of innate and adaptive immunity cross-talk (Subbarayan et al., 2020; Earls et al., 2019; Sanchez-Guajardo et al., 2013).