Biomarker: F315-IgE Green Bean

Overview

Green bean is the immature pod of Phaseolus vulgaris, a legume consumed as a vegetable. F315-IgE evaluates IgE antibodies directed against green bean proteins and may support assessment of IgE-mediated sensitization associated with ingestion, handling, or inhalation of raw green bean material. Reported reactions include oral or systemic food allergy and, less commonly, respiratory symptoms after exposure to raw green beans or cooking vapors. Serum-specific IgE testing may help evaluate suspected sensitization, but a positive result does not by itself establish clinical allergy.

Clinical Use Cases

Evaluation of suspected green bean allergy: Supports investigation of immediate symptoms such as urticaria, angioedema, gastrointestinal symptoms, wheezing, or anaphylaxis occurring after green bean exposure.
Serum-specific IgE assessment: Measures IgE antibodies against green bean extract in a blood sample when the clinical history suggests relevant exposure.
Evaluation of inhalational or occupational-type exposure: May be considered when asthma or rhinitis occurs during handling, preparation, or exposure to raw green beans. Human case reports have documented positive serum-specific IgE in this setting.
Correlation with clinical history: Results should be interpreted with the timing, reproducibility, route of exposure, quantity consumed, food preparation, and symptoms associated with exposure.
Assessment alongside other allergy testing: Serum-specific IgE may be used with skin testing and, when results remain uncertain, a medically supervised oral food challenge. Testing alone does not distinguish asymptomatic sensitization from symptomatic allergy.
Evaluation of related food sensitization: Testing may be considered alongside selected legume allergens when the history suggests possible co-sensitization or cross-reactivity, although positive tests to multiple legumes do not necessarily indicate clinical allergy to each one.

Specimen Types

Serum: Commonly used for measurement of green bean-specific IgE in blood.
Plasma or whole blood: May be accepted by some validated laboratory methods, depending on the assay and laboratory protocol.

Measurement Methods

Allergen-specific IgE testing: In-vitro immunoassays measure IgE antibodies directed against green bean extract in serum or another validated blood specimen. F315 is an extract-based green bean allergen designation.
Component-resolved diagnostics: Research has identified potential green bean IgE-binding proteins, including a nonspecific lipid transfer protein associated with approximately 9 kDa molecular weight in a small group of patients. Routine component testing specifically validated for green bean is limited, so these findings should not be treated as a substitute for established extract-based testing.
Immunoblotting: Used primarily in research to characterize IgE-binding green bean proteins, including proteins detected in raw and cooked extracts. It is not generally the primary clinical test for routine evaluation.
Skin testing and oral food challenge: Skin-prick or prick-to-prick testing can provide additional clinical information, while a medically supervised oral food challenge may be used when the diagnosis remains uncertain. These approaches assess clinical reactivity and should be interpreted with the history rather than used in isolation.

Test Preparation and Influencing Factors

Fasting: Blood collection for serum-specific IgE generally does not require fasting.
Medications: Antihistamines can interfere with skin testing, but they generally do not prevent measurement of serum-specific IgE. Medication changes should follow clinician instructions.
Total IgE concentration: Very high total IgE may be associated with multiple positive specific-IgE results that are not clinically relevant. Total IgE should be considered during interpretation.
Timing after exposure: The relationship between exposure and symptoms is important for clinical interpretation. A blood test may remain positive regardless of whether symptoms occurred during the most recent exposure.
Food preparation: Raw and cooked green bean may expose individuals to different allergenic proteins. Respiratory reactions reported with raw green bean exposure were not reproduced with cooked green bean in one case series, whereas other patients reacted to cooked green bean ingestion.
Age and clinical context: The meaning of a specific-IgE concentration varies with age, pretest probability, symptoms, atopic disease, and exposure history.
Cross-reactive sensitization: IgE binding to homologous proteins from other legumes or plant foods can produce a positive result without clinically relevant green bean allergy.
Sensitization versus allergy: Detectable green bean-specific IgE indicates immunologic sensitization. It does not prove that green bean causes symptoms, predict reaction severity, or establish that green bean must be excluded from the diet.

Cross-Reactivity

Legumes: Green bean belongs to the Fabaceae family, which includes peanut, soybean, peas, lentils, chickpeas, and other beans. Immunologic cross-reactivity among legumes can occur, but human challenge studies indicate that clinically important cross-allergy is less common than laboratory cross-reactivity.
Storage proteins: Homologous 7S and 11S globulin proteins may contribute to co-sensitization among legumes. Co-sensitization, however, does not consistently correspond to clinical reactions to each legume.
Nonspecific lipid transfer protein: A green bean lipid transfer protein has been identified in patients with documented reactions to cooked green bean, and its IgE binding was inhibited by peach Pru p 3 in laboratory studies involving human sera. This supports immunologic cross-reactivity involving plant lipid transfer proteins, but it does not establish that every person sensitized to a lipid transfer protein will react to green bean.
Clinical relevance: Positive IgE tests to green bean and other legumes should not be interpreted as proof of multiple food allergies. Clinical history and, when appropriate, supervised challenge testing are needed to determine whether cross-sensitization is clinically meaningful.