Study of chemotactic activity developed by neutrophils from rheumatoid arthritis patients.

Neutrophils are the predominant cells accumulated in the synovial fluid (SF) of rheumatoid arthritis (RA) patients. Accumulation of neutrophils may be regarded as a possible way by which neutrophils exert cytotoxic functions. The aim of the present study was to analyze the chemotactic response of neutrophils (PMNs) isolated from the peripheral blood or SF of patients with RA by performing the chemotaxis assay, in which N-formyl-methionyl-leucyl-phenylalanine (FMLP) was used as chemotactic agent.

Interaction of human immunoglobulin G with CD16 on natural killer cells: ligand clearance, FcgammaRIIIA turnover and effects of metalloproteinases on FcgammaRIIIA-mediated binding, signal transduction and killing.

Human natural killer (NK) cells express low-affinity Fc immunoglobulin G (IgG) receptor (FcgammaRIIIA/CD16). The binding of monomeric IgG (mIgG) and F(ab')(2) fragments of 3G8 anti-CD16 monoclonal antibody (mAb) to FcgammaRIIIA was investigated by flow cytometry. Over 90% of NK cells bound endogenous IgG, and during incubation at 37 degrees C, the FcgammaRIIIA occupancy decreased slowly.

Human NK cells express Fc receptors for IgA which mediate signal transduction and target cell killing.

Receptors for the Fc region of IgG (FcgammaRIIIa, FcgammaRIIc) and IgM (FcmicroR) were previously described on NK cells. In this work the expression of Fc receptors for IgA (FcalphaR) on human NK cells and the signaling events were investigated. The FcalphaR was demonstrated by flow cytometry using secretory IgA (sIgA) and anti-human IgA antibody.

Phospholipase A2 modulates respiratory burst developed by neutrophils in patients with rheumatoid arthritis.

Activated by bacterial peptides, phorbol esters, calcium ionophores and other agonists, neutrophils (PMNs) release the proinflammatory mediator, arachidonic acid (AA) via the intervention of phospholipase A(2) (PLA(2)). AA may play an essential role in activation of NADPH-oxidase, which is involved in the generation of superoxide anion by neutrophils. The present study is focused on the involvement of PLA(2) in the respiratory burst developed by PMNs isolated from patients with rheumatoid arthritis (RA).

IgA monoclonal and polyclonal proteins as regulatory factors of the NK cytotoxic activity.

The presence of receptors for IgA (IgAR) on natural killer (NK) cells was only indirectly suggested yet. To elucidate the presence of IgAR on NK cells and its possible role in modulation of the NK activity, was initiated a preliminary study carried out in a homologous system, using human non adherent lymphocytes (NAL) and human seric or secretory IgA. A proportion of over 20% NK cells (CD16+ CD56+) was determined by flow-cytometry in the NAL-cells population.