RESUMEN
A study was made of the ability of purified human C-reactive protein (CRP) in pentameric (pCRP) and subunit (sCRP) form to induce the production of tumour necrosis factor alpha (TNF-alpha) in macrophage-like cell line P388D1, as well as the combined effects of CRP and recombinant human TNF-alpha on the proliferation of L929 cell line. Both pCRP and sCRP induced TNF production by P388D1 cells, pCRP was inhibitory per se for L929 cells, while sCRP was not, when present in cultures for 72 h without actinomycin D (AD). In the presence of AD, sCRP was inhibitory as well, even when the period of incubation was reduced to 18 h. The presence in CRP of melittin-like sequence known to be responsible for the activation of cellular phospholipases is shown herein. Together with literature data, indication that CRP does influence the catalytic activity of purified phospholipase D, suggests that CRP exerts effect on P388D1 and L929 cells via regulation of cell phospholipases. The results also indicate that TNF effects in vivo can be modulated in different ways by conformational variants of CRP, whose occurrence and ratio depend on a phase of inflammatory reaction.