Characterization of Phl p 4, a major timothy grass (Phleum pratense) pollen allergen.
BACKGROUND
Group 4 grass pollen allergens represent glycoproteins with a molecular weight of 50 to 60 kd, which are present in many grass species. Almost 75% of patients allergic to grass pollen display IgE reactivity to group 4 allergens, which hence can be regarded as major grass pollen allergens.


OBJECTIVE
In this study attempts were made to obtain information regarding the immunologic properties, localization, and occurrence of Phl p 4 and related allergens.


METHODS
Phl p 4 was detected in timothy grass pollen extracts by immunoblotting with serum IgE and monoclonal antibodies and was localized in pollen by immunoelectron microscopy. A peptide sequence from Phl p 4 was obtained by amino acid sequencing. The resistance of Phl p 4 against trypsin was analyzed after trypsin treatment of timothy grass pollen extracts with serum IgE and monoclonal antibodies. Cross-reactivities between Phl p 4 and Amb a 1, the major allergen of ragweed, were studied by using monoclonal antibodies and by IgE- inhibition studies.


RESULTS
Phl p 4 was characterized as a trypsin-resistant major timothy grass pollen allergen. By immunoelectron microscopy Phl p 4 was localized in the exine, cytoplasm, and amyloplast of timothy grass pollen. significant sequence similarities of a Phl p 4 10 amino acid peptide with Amb a 1, the major ragweed allergen, could be found. The immunologic similarity of Phl p 4 and Amb a 1 was confirmed by cross-reactivity of monoclonal antibodies and patients' IgE.


CONCLUSIONS
Phl p 4 represents a trypsin-resistant major timothy grass pollen allergen with immunologic similarities to the major ragweed allergen Amb a 1 and therefore must be considered an important cross-reactive component in grass pollen and weed pollen allergy.
Fischer
S
S
Institute of General and Experimental Pathology, University of Vienna, Austria.
Grote
M
M
Fahlbusch
B
B
Müller
W D
WD
Kraft
D
D
Valenta
R
R
D000485:Allergens / Q000737:chemistry* / Q000276:immunology / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000737:chemistry; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D052179:Antigens, Plant; D001666:Binding Sites, Antibody; D015153:Blotting, Western; D003285:Contractile Proteins; D006801:Humans; D007073:Immunoglobulin E / Q000737:chemistry / Q000378:metabolism; D008840:Microfilament Proteins / Q000276:immunology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009842:Oligopeptides / Q000276:immunology; D010940:Plant Proteins / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification* / Q000648:ultrastructure; D006109:Poaceae / Q000737:chemistry / Q000276:immunology* / Q000648:ultrastructure; D011058:Pollen / Q000737:chemistry / Q000276:immunology* / Q000648:ultrastructure; D051304:Profilins; D014357:Trypsin / Q000494:pharmacology
D000485:Allergens; C026967:Amb a I protein, Ambrosia artemisiifolia; D000911:Antibodies, Monoclonal; D052179:Antigens, Plant; D003285:Contractile Proteins; D008840:Microfilament Proteins; D009842:Oligopeptides; C100980:Phl p 4 protein, Phleum pratense; D010940:Plant Proteins; D051304:Profilins; C074244:Amb a II protein, Ambrosia artemisiifolia; D007073:Immunoglobulin E; D014357:Trypsin