The CD11a partner in Sus scrofa lymphocyte function-associated antigen-1 (LFA-1): mRNA cloning, structure analysis and comparison with mammalian homologues

The porcine-LFA-1 CD11a (alpha) subunit coding sequence was cloned, sequenced and compared with the available mammalian homologues in this study. Despite some focal differences, it shares all the main characteristics of these latter. Interestingly, as in sheep and humans, an allelic variant with a triplet insertion resulting in an additional Gln-744 was consistently identified, which suggests an allelic polymorphism that might be biologically relevant.Together with the pig CD18-encoding cDNA, which has been available for a long time, the sequence data provided here will allow the successful expression of porcine CD11a, thus giving the first opportunity to express the Sus scrofa beta2-integrin LFA-1 in vitro as a tool to examine the specificities of inflammation in the porcine species.Integrins constitute a large family of adhesion molecules with important roles in cell-extracellular matrix and cell-cell interactions which condition both the maintenance of tissue integrity and the promotion of cellular migration. They are heterodimeric membrane glycoproteins composed of non-covalently associated single-pass transmembrane α and β subunits, which are expressed on a wide range of cells [1]. The biggest part of each integrin subunit is extracellular while transmembrane region and cytoplasmic tail are typically reduced. The N-terminal domains of the α and β subunits associate to form the integrin headpiece, which contains the ligand binding site. The C-terminal segments traverse the plasma membrane and mediate interactions with the cytoskeleton and with signalling proteins [2,3].Among the integrins, the leukocyte-specific β2-integrins (CD11/CD18) include four members: (i) CD11a/CD18 (LFA-1, αLβ2) on all leukocytes ; (ii) CD11b/CD18 (Mac-1, CR3, αMβ2) mainly on myeloid cells ; (iii) CD11c/CD18 (gp150/95, CR4, αXβ2, Leu-M5) and (iv) CD11d/CD18 (αDβ2) on monocytes and macrophages [4]. The individuals lacking functional β2 integrins due to mutations in the β2 (CD18) subunit d