Increased IL-13 but not IL-5 production by CD4-positive T cells and CD8-positive T cells in multiple sclerosis during relapse phase

In the present study, we flow cytometrically analyzed the intracellular production of interleukin (IL)-5 and IL-13 in peripheral blood CD4⁺ and CD8⁺ T cells from patients with multiple sclerosis (MS), human T-lymphotropic virus type I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and healthy controls. IL-13-producing T cells were significantly increased in both T cell subsets in MS at relapse, markedly in the conventional form of MS and modestly in the optocospinal form of MS, and returned to normal at remission. However, IL-5-producing T cells did not vary regardless of clinical phase or type. HAM/TSP showed no significant change in the number of IL-5- and IL-13-producing cells. A distinct profile of IL-13 and IL-5 production by disease and by phase of MS suggests an active involvement of these type 2 cytokines in central nervous system (CNS) inflammation.