Rheumatoid factor

Rheumatoid factor (RF) is the autoantibody (antibody directed against an organism's own tissues) that was first found in rheumatoid arthritis. It is defined as an antibody against the Fc portion of IgG (an antibody against an antibody). RF and IgG join to form immune complexes that contribute to the disease process.

Rheumatoid factor can also be a cryoglobulin (antibody that precipitates on cooling of a blood sample); it can be either type 2 (monoclonal IgM to polyclonal IgG) or type 3 (polyclonal IgM to polyclonal IgG) cryoglobulin.

Although predominantly encountered as IgM, rheumatoid factor can be of any isotype of immunoglobulins, i.e. IgA, IgG, IgM, IgE, IgD.

Testing

RF is often evaluated in patients suspected of having any form of arthritis even though positive results can be due to other causes, and negative results do not rule out disease. But, in combination with signs and symptoms, it can play a role in both diagnosis and disease prognosis. It is part of the usual disease criteria of rheumatoid arthritis.

RHF

RHF may refer to:

Rhodium hexafluoride

Rhodium hexafluoride, also rhodium(VI) fluoride, (RhF₆) is the inorganic compound of rhodium and fluorine. A black volatile solid, it is a highly reactive material, and a rare example of a rhodium(VI) compound.

Synthesis, structure, properties

Rhodium hexafluoride is prepared by reaction of rhodium metal with an excess of elemental fluorine:

The RhF₆ molecule has octahedral molecular geometry. Consistent with its d³ configuration, the six Rh–F bond lengths are equivalent, being 1.824 Å. It crystallises in an orthorhombic space group Pnma with lattice parameters of a = 9.323 Å, b = 8.474 Å, and c = 4.910 Å.

Like some other metal fluorides, RhF₆ is highly oxidising. It attacks even glass even in the absence of water. It can even react with elemental oxygen.

References