TLR-4, the main receptor for LPS recognition, was significantly expressed on CD4+CD28null T cells in AS (23.1 ± 21.9% versus 0.9 ± 1.2%), in PsA (12.4 ± 18.1% versus 0.4 ± 0.5%) and in RA (23.1 ± 24.7% versus 0.6 ± 0.9%; each with P < 0.001). Here, CD4 is linked to rheumatoid arthritis.