Alpha Lactalbumin, F76

An allergen is a substance that triggers an allergic reaction. In atopic diseases, allergens stimulate the production of IgE antibodies and are clinically relevant causal factors in the development of allergic symptoms. Measuring allergen-specific IgE in blood confirms the allergen’s role in a type I (IgE-mediated, immediate) hypersensitivity reaction and helps identify the most likely causative allergen, as well as select appropriate therapeutic and preventive measures.

An allergenic substance typically contains not one but several protein structures (components) that can act as allergens. Some are major (primary) allergens, others are minor (secondary). Component-resolved diagnostics helps distinguish true sensitization from cross-reactivity.

Food allergy is a reaction that occurs after ingestion of food and is mediated by immune mechanisms. It is often confused with food intolerance, which is due to other causes (food preparation characteristics, product composition, metabolic disorders, gastrointestinal diseases). Food allergy is more common in young children, particularly under 3 years of age.

One of the most common food allergens is milk. In children sensitized to cow’s milk proteins, allergy may present not only with cutaneous symptoms but also with gastrointestinal involvement, rhinitis, exacerbations of bronchial asthma, and anaphylactic reactions. Hypersensitivity to cow’s milk does not always resolve in childhood and may persist into adulthood for many years or lifelong.

Cow’s milk contains approximately 40 proteins with allergenic potential. Based on physicochemical properties, they are classified into caseins (about 80% of milk proteins) and whey proteins (about 20%). Whey predominantly contains globular proteins—β-lactoglobulin and α-lactalbumin—as well as smaller amounts of bovine serum albumin, lactoferrin, and immunoglobulins. α-Lactalbumin and β-lactoglobulin are synthesized in the mammary gland, whereas bovine serum albumin, lactoferrin, and immunoglobulins originate from blood.

Antibody responses to milk proteins vary substantially among individuals; therefore, a single “main” cow’s milk allergen cannot be identified. In most cases, specific IgE is detected to several proteins simultaneously, and major allergens most commonly include casein (Bos d 8), β-lactoglobulin (Bos d 5), and α-lactalbumin (Bos d 4).

α-Lactalbumin is a monomeric globular calcium-binding protein with a molecular weight of 14.2 kDa; it accounts for about 25% of whey proteins and approximately 5% of total milk proteins. In secretory cells of the mammary gland, α-lactalbumin participates in regulating lactose synthesis. The structure of bovine α-lactalbumin is approximately 72% similar to the human protein; antibacterial and immunostimulatory properties have been described, making it a relevant component of infant nutrition. Specialized formulas exist in which α-lactalbumin content is increased and β-lactoglobulin content is reduced.

Protein allergenicity is largely determined by conformational structure. Cross-reactivity of α-lactalbumin with similar proteins from the milk of other animal species is possible but insufficiently studied. In some cases, IgE cross-reactivity to β-lactoglobulin and α-lactalbumin has been reported.

IgE participates in immediate hypersensitivity reactions. Elevated total serum IgE may be found in various allergic diseases, helminth infections, certain autoimmune conditions, hyper-IgE syndrome, and some viral infections. Measuring allergen-specific IgE in blood is one of the main methods for defining the spectrum of clinically relevant allergens in immediate-type allergy. Each allergen has a corresponding specific IgE. The purpose of this test is to detect specific IgE to α-lactalbumin.

Preparation for testing
To obtain reliable results (including for glucose, cholesterol, and triglyceride testing), it is recommended to avoid fatty foods, concentrated sweets, and alcohol on the day before sampling.

Blood testing should be postponed immediately after instrumental investigations (e.g., X-ray, CT, MRI) and physiotherapy procedures, as these may affect test results.