The human NK gene complex encodes for the leucocyte C-type lectins, CD69, AICL (activation-induced C-type lectin), LLT1 (lectin-like transcript), CD161/NKR-P1A, CD94, and for NKG-2 molecules. These gene products have been implicated in the regulation of the function of natural killer (NK) cells and other lymphocytes. In this study the expression of C-type lectins during the early activation of PMA-stimulated peripheral blood lymphocytes was examined. To investigate the in¯uence of de novo protein synthesis on activation-dependent expression of C-type lectins, cells were cultured in presence of cycloheximide (CHX) and mRNA levels were analyzed by semi-quantitative reverse transcription-polymerase chain reaction. Upregulated levels of CD69, AICL, and LLT1, but less pronounced changes of CD161/NKR-P1A and CD94 mRNA were found at early time points of cellular activation. CD69 was superinduced by CHX at the nuclear precursor transcript and the mRNA level suggesting that regulation of transcriptional activity and mRNA stability contribute to extent of CD69 mRNA accumulation. CHX treatment resulted also in an overexpression of AICL, LLT1, and CD161/NKR-P1A mRNAs. Conversely, CHX blocked CD94 mRNA expression in PMA-stimulated cells, demonstrating that this process is dependent on new protein synthesis. Expression kinetics in context with susceptibility to CHX indicate that the mechanisms responsible for upregulated CD69, AICL, and LLT1 expression are distinct from those which control CD161/NKR-P1A or CD94 expression.
Two monoclonal antibodies (Mabs) binding to a toxic extracellular metallo‐proteinase of Aeromonas salmonicida subsp. achromogenes, AsaP1, were produced. Both reacted with common epitopes of the native enzyme and recognized this 20 kDa antigen on Western blots. One of these Mabs had an inhibitory effect on the caseinase activity of the exotoxin. A Mab‐based ELISA was set up and evaluated for serological detection of AsaP1 in bacterial culture filtrates. The exotoxin was identified serologically in the extracellular products of 11 of 26 atypical Aer. salmonicida isolates, including the type strain for subsp. achromogenes NCIMB 1110. The ELISA was approximately 100‐fold more sensitive in detecting AsaP1 compared with an azocasein assay. The established serological test enables AsaP1 to be quantified reliably with a lower detection limit of about 0·12 ng ml−1 and has a potential use for the phenotypic differentiation of atypical Aer. salmonicida isolates.
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