What antinuclear antibody isotype most likely indicates systemic lupus erythematosus?

The isotype most commonly associated with systemic lupus erythematosus (SLE) is IgG. In SLE, the presence of antinuclear antibodies (ANAs) is a key laboratory finding. Specifically, IgG antibodies are typically found at higher levels and are considered significant markers in the diagnosis and monitoring of this autoimmune condition.

IgG is known for its ability to form immune complexes that can contribute to tissue damage and inflammation, which are hallmark features of SLE. The detection of IgG ANAs can provide valuable information regarding the activity of the disease, as well as its potential severity.

While other isotypes like IgA, IgD, and IgM also play roles in immune responses, they are less specifically associated with SLE. IgM antibodies, for instance, may be more prevalent in acute infections or other autoimmune diseases but lack the specificity linked to the chronic autoimmune attacks seen in SLE. Thus, the presence of IgG is predominantly used as a diagnostic criterion for SLE.