CD18, the common beta subunit of beta2-integrins, associates with four distinct alpha chains to give rise to four different beta2-integrins: CD11a/CD18 (LFA-1), CD11b/CD18 (Mac-1), CD11c/CD18 (CR4), and CD11d/CD18. Previously, we and others showed that CD18 of LFA-1 serves as a receptor for Mannheimia haemolytica leukotoxin (Lkt). Level of expression of Mac-1 is higher than that of LFA-1 and other beta2-integrins on polymorphonuclear leukocytes (PMNs), which constitute the leukocyte subset most susceptible to Lkt. Hence, it is likely that CD18 of Mac-1 also mediates Lkt-induced cytolysis. Co-expression of CD11b and CD18 of cattle on Lkt-resistant cells is necessary to irrefutably demonstrate the role of Mac-1 in Lkt-induced cytolysis. This approach is hindered by lack of availability of complete sequence of cattle CD11b. Therefore, in this study, we cloned and sequenced the full length cDNA encoding cattle CD11b. The 3459 bp cDNA of cattle CD11b encodes a polypeptide of 1152 amino acids. The deduced amino acid sequence of CD11b of cattle exhibits 75% identity to that of humans and chimpanzees, 74% identity to that of dogs, and 70% identity to that of mice and rats. Availability of cattle CD11b cDNA should facilitate the elucidation of Lkt-receptor interactions in cattle and other species.
"The PCR strategy to obtain the full length porcine CD11b cDNA is shown in Fig. 1. FP1 and RP1 primers were designed based on the cow cDNA sequence (AY841169) (Gopinath et al., 2006). To obtain both 5 -and 3 -end sequences, two additional pairs of primers were designed. "
[Show abstract][Hide abstract] ABSTRACT: CD11b (α(M)) is a cell-surface glycoprotein mainly expressed on myeloid cells, required for important interactions during the immune response and involved in the pathogenesis of several diseases. The full length cDNA encoding porcine CD11b protein has been cloned and sequenced. Pig CD11b cDNA sequence contains an ORF of 3459 nucleotides that encodes a deduced polypeptide of 1152 amino acid residues that share with CD11b from other species: High % amino acid identity, common domains (α-I, Ca(++) binding, MIDAS), N-glycosylation sites, and the seven FG-GAP tandem repeats. Real time quantitative PCR expression analysis revealed that CD11b transcripts were highly expressed in neutrophils, showing a lower expression in spleen. The CD11a-CD11b-CD11c gene cluster locates on the porcine chromosome region SSC3p15-17.
[Show abstract][Hide abstract] ABSTRACT: Leukotoxin (Lkt) is the primary virulence factor secreted by Mannheimia haemolytica which causes pneumonia in ruminants. Previously, we have shown that CD18, the beta subunit of beta(2) integrins, mediates Lkt-induced cytolysis of ruminant leukocytes. CD18 associates with four distinct alpha subunits giving rise to four beta(2) integrins, CD11a/CD18 (LFA-1), CD11b/CD18 (Mac-1), CD11c/CD18 (CR4), and CD11d/CD18. It is not known whether all the beta(2) integrins serve as a receptor for Lkt. Since PMNs are the leukocyte subset that is most susceptible to Lkt, and Mac-1 expression on PMNs exceeds that of other beta(2) integrins, it is of interest to determine whether Mac-1 serves as a receptor for Lkt which necessitates the cloning of CD11b and CD18. In this study, we cloned and sequenced the cDNA encoding CD11b of Ovis canadensis (bighorn sheep) and Ovis aries (domestic sheep). CD11b cDNA is 3455 nucleotides long encoding a polypeptide of 1152 amino acids. CD11b polypeptides from these two species exhibit 99% identity with each other, and 92% with that of cattle, and 70-80% with that of the non-ruminants analyzed.
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