CD28 and melanoma: Presence of serum CD28 abs correlated significantly with the type of disease and was higher in patients with melanoma (42/230 = 18.3%) and patients with viral hepatitis (45/212 = 21.2%) (p<0.001, Chi-square-test) compared to patients with allergies (11/149 = 7.4%), multiple myeloma (4/46 = 8.7%), psoriasis (3/78 = 3.85%) or healthy blood donors (2/140 = 1.4%) (Figure 3).