CD4 and juvenile idiopathic arthritis: In other forms of JIA (e.g. oligo-, poly- and spondyloarthritis) both indicators of innate immunity, such as elevated myeloid-related proteins (MRP) 8 and 14 produced by neutrophils and infiltration by neutrophils, monocytes and macrophages, and indicators of adaptive immunity, such as prominent CD4 lymphocyte infiltration, are found directly in the synovium and synovial fluid[14,15].