TNF and rheumatoid arthritis: Treatment of human monocytes with 1:1 mixture of huLTF and RA-IgG (RA-IgG-IC) resulted in significant TNF-α secretion compared to that treated with huLTF, RA-IgG or a mixture of huLTF with normal IgG (IVIG), which is similar to that cultured in medium alone (Fig. 2B).