Rheumatoid factors are immunoglobulins directed against:
The Fc poion of immunoglobulin G (IgG)
The Fc poion of immunoglobulin G (IgG)
The Fc poion of immunoglobulin A (IgA)
The Fc poion of immunoglobulin M (IgM)
The Fc poion of immunoglobulin D (IgD)