PubMed · 5251663
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R E Reisman. 1969. Delayed hypersensitivity to merthiolate preservative.. https://doi.org/10.1016/0021-8707(69)90067-7
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Surfactant protein D (SP-D) is considered to play an important role in innate immunity in the lungs by binding, via its multiple C-type lectin domains, to carbohydrate structures present on a range of viruses, bacteria, yeasts and fungi. The resulting agglutination of the target pathogens provides host defence which can be further enhanced by killing and clearance mechanisms mediated by phagocytic cells which carry receptors for SP-D. Recent findings suggest that SP-D, and the structurally related lung surfactant protein A (SP-A), may also modulate allergic reactions by binding certain glycosylated allergens. The finding of SP-D at a variety of other sites besides the lungs, such as the gastric mucosae, is suggestive that it may play a general protective role in several secretions.
Cockroaches produce potent allergens that are an important cause of asthma. The two principal domiciliary cockroach species, Blattella germanica and Periplaneta americana, secrete major allergens, Bla g 1 and Per a 1. Here, we report the molecular cloning of three Bla g 1 cDNA clones, which showed 70% amino acid sequence identity with Per a 1. Plaque immunoassays with human IgE antibodies or murine monoclonal antibodies showed that these allergens were antigenically cross-reactive. The Bla g 1 sequences also showed homology to five previously undefined cockroach allergen sequences. An unusual feature of all these sequences was that they contained multiple tandem amino acid repeats of approximately 100 amino acid residues. Between one and seven repeat units were identified by dot-plot matrix analysis. The sequences also showed homology to a mosquito protein involved in digestion (ANG12 precursor) and to mitochondrial energy transfer proteins. High levels of Bla g 1 were found in cockroach hindgut and proventriculus. Amino acid sequencing of natural Bla g 1 and Per a 1 suggested that these allergens are cleaved by trypsin-like enzymes following secretion into the digestive tract. The repeat sequences appear to have evolved by duplication of an ancestral amino acid domain, which may have arisen from the mitochondrial energy transfer proteins.
The dermatophyte fungus Trichophyton exhibits unique immunologic properties by its ability to cause both immediate and delayed type hypersensitivity. An 83-kDa Trichophyton tonsurans allergen (Tri t 4) was previously shown to elicit distinct T lymphocyte cytokine profiles in vitro. The homologous protein, Tri r 4, was cloned from a Trichophyton rubrum cDNA library, and the recombinant protein was expressed in Pichia pastoris. This 726-amino acid protein contained an arrangement of catalytic triad residues characteristic of the prolyl oligopeptidase family of serine proteinases (Ser-Asp-His). In addition, a novel Trichophyton allergen, encoding 412 amino acids, was identified by its human IgE antibody-binding activity. Sequence similarity searches showed that this allergen, designated Tri r 2, contained all of the conserved residues characteristic of the class D subtilase subfamily (41-58% overall sequence identity). Forty-two percent of subjects with immediate hypersensitivity skin test reactions to a Trichophyton extract exhibited IgE antibody binding to a recombinant glutathione S-transferase fusion protein containing the carboxyl-terminal 289 amino acids of Tri r 2. Furthermore, this antigen was capable of inducing delayed type hypersensitivity skin test reactions. Our results define two distinct antigens derived from the dermatophyte Trichophyton that serve as targets for diverse immune responses in humans.