C4A and hereditary spastic paraplegia: The present study measured the immunoglobulins IgG, IgM, IgA, IgE, complements C3 and C4, T lymphocyte subgroup, B cells, NK cells and C-reactive protein (CRP) in the acute phase of HSP and compared with patients with HSP with different clinical symptoms; hence, this study aimed to find a connection between cellular, humoral immunity, and HSP pathogenesis.