PubMed · 4772555
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L P Durocher, M Lassonde. 1973. [Contact dermatitis].. https://pubmed.ncbi.nlm.nih.gov/4772555/
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Group 3 allergens of the genus Dermatophagoides represent one of the major groups of house dust mite allergens. The cDNA sequence data for Der p 3, in combination with both N-terminal amino acid sequences and substrate affinity data, have confirmed that the group 3 allergens are trypsin-like proteases. Using the information from the Der p 3 P3WS1 cDNA clone, genes encoding both Der f3 and Der p 3 have now been amplified by the polymerase chain reaction and analysed. Two Der f3 clones and three Der p 3 genomic clones were sequenced. Each of the clones contained a single small intron and encoded a mature protein of 233 amino acids. The nucleotide sequence was identical for both Der f3 clones. There was 81% identity between the Der f3 sequence and the original Der p 3 P3WS1 clone. The calculated molecular weight of Der f3 was 25.27 kDa compared to 24.98 kDa for Der p 3. All the amino acid residues required for the catalytic activity and the substrate specificity were conserved between the two homologues. The coding sequences of two of the three Der p 3 genomic clones were identical to the original Der p 3 P3WS1 clone with the third having nucleotide changes resulting in four non-conservative amino acid substitutions in the mature protein. These substitutions resulted in a molecule with a slightly larger molecular weight and a more acidic pI value than the original Der p 3 clone. This third Der p 3 genomic clone is, therefore, an isoform of the Der p 3 P3WS1 clone and is classified as an isovariant of the allergen. The nucleotide sequence data presented are the first reported for Der f 3. The Der f 3 gene, like the Der p 3 gene, encoded a trypsin-like protease, but with a slightly larger molecular weight.
The major allergens of Parietaria officinalis were characterized with a panel of nine monoclonal antibodies (mAbs). The binding of mAbs and patients' IgE in Western blots revealed two proteins with similar molecular weights in the range of 8-10 kD. Analysis of the mAb-binding patterns in Western blots of P. officinalis extract under reducing and nonreducing conditions allows the mAbs to be divided into three different groups. mAbs of group I recognize the higher-molecular-weight component (9.4 kD), mAbs of group II recognize the lower component (8.8 kD) and mAbs of group III recognize both proteins. A comparable mAb-binding pattern was observed with Western blots of Parietaria judaica. The mAbs were used for affinity purification of the corresponding proteins from a P. officinalis extract. The purified proteins obtained with mAbs of group I-III inhibit the binding of patients' IgE (serum pool) to a high degree, indicating that they posses the major IgE-reactive epitopes. The affinity-purified proteins were subjected to SDS-PAGE, blotted and immunologically stained by mAb binding. The results confirmed those obtained with the complete extracts. The N-terminal amino acid sequences of the blotted proteins were analyzed. The sequences of all the proteins contained highly conserved regions: GGVV (positions 4-7) and MPPLL (positions 11-15), alternating with highly variable regions (positions 1-3 for group II and 8-10 for group I). A specific group I sequence appears to be at position 1-3 with the amino acids APA and a specific group II sequence appears to be at position 8-10 with the amino acids GAL. It is possible that the two similar proteins are isoforms of Par o 1.
Parasitic helminths cause enormous morbidity among humans especially in developing countries. These large extracellular organisms have complex life cycles frequently involving an arthropod vector. Helminth parasites can be tissue dwelling or intestinal but all induce a dramatic expansion of the Th2 lymphocyte subset. It remains unclear whether these Th2-derived responses, including IgE, eosinophilia and mastocytosis are important in the protective immune response to the parasite, or are responsible for immune-mediated pathology, or both. Interestingly, despite high levels of IgE and other features of Th2 cell activation, allergic responses are rarely observed in infected individuals. Helminths can survive for years in the infected host, and have evolved elaborate immune evasion strategies to establish these long-lived infections including the induction of tolerance to parasite antigens. This review discusses the dynamics of infection with helminth parasites with specific emphasis on Th2 subset activation. The current knowledge of immune effector mechanisms, immunopathology and hopes for vaccine development are also discussed.