The specificity and isotypic profile of humoral immune responses to Dactylis glomerata (Cocksfoot) pollen was studied by isoelectric focusing (IEF)-immunoprint analysis using 26 human plasma samples with high levels of Dactylis pollen-specific IgG4 (IgG4+ plasma) and 25 human plasma samples with low levels of specific IgG4 (normal plasma). Over 60 individual protein components in an aqueous pollen extract were separated by IEF and immunoprinted onto nitrocellose (NC). Following plasma incubation, bound IgE, IgG1-4, IgA1, IgA2 and IgM antibodies were detected on separate immunoprints with isotype-specific antibodies. Binding patterns of IgG4 and the majority of IgG1 and IgA2 antibodies in the IgG4+ plasma group very closely paralleled the binding patterns produced by the IgE antibodies from the same plasma and are described as the 'allergen repertoire'. In contrast, IgE, IgG4, IgG1 and IgA2 antibody reactivities to the 'allergen repertoire' were insignificant in the normal plasma group. These results suggest a qualitative, as well as a quantitative relationship between the immune responses which involve these 4 isotypes. Characteristic IgG2 and IgM antibody binding patterns, predominantly to non-allergenic antigens, were shared by the plasma from both groups, while IgG3 and IgA1 antibody binding patterns were highly variable from one plasma to another in both groups. One possible origin of the allergic diseases at the immunoglobulin heavy chain gene level is discussed.