CD28 and rheumatoid arthritis: This study enriched a series of pathways related to immune system, including altered T cell and B cell signaling in rheumatoid arthritis, calcium-induced T lymphocyte apoptosis, cd28 signaling in T helper cell, icos signaling in T helper cells, nur77 signaling in T lymphocytes, T helper cell differentiation, B cell development, crosstalk between dendritic cells, and natural killer cells.