Partial characterization of red gram (Cajanus cajan L. Millsp) polypeptides recognized by patients exhibiting rhinitis and bronchial asthma

Abstract

We sought to assess the allergenic potential of red gram by identifying and characterizing the responsible proteins. Immunoblotting was performed to detect IgE binding proteins. Identities of these proteins were confirmed by mass spectrometry. To evaluate allergenic potential, BALB/c mice were sensitized with red gram proteins and levels of specific immunoglobulins, histamine, Th2 cytokines were measured. Allergenic response was evident by significant increase in specific IgE, IgG1, histamine and Th2 cytokine levels. Prominent anaphylactic symptoms, discernible histopathological responses and down regulation of IFN-γ levels give strong support towards allergenicity of red gram proteins. IgE immunoblot detected five proteins; one of 66kDa, three of 45kDa (pI of ∼5.3, 5.9 and 6.6) and one of 30kDa. All these proteins showed homology to known allergens of soybean (different subunits of β-conglycinin), lentil (Len c1 and Len c2), peanut (Ara h1) and pea (vicilin). In conclusion, five novel IgE binding proteins (namely Caj c1, Caj c2, Caj c3, Caj c4 and Caj c5) were identified as putative clinically relevant allergens.