Characterisation of Bovine Leukocyte Ig-like Receptors

Louise Hogan,John Trowsdale,Philip Butcher,Mahavir Singh,Sabin Bhuju,Rachel L Allen,Des C Jones,Martin Vordermeier,Ken Laing,Nikolas Nikolaidis

doi:10.1371/journal.pone.0034291

Abstract

Leukocyte Immunoglobulin-like receptors (LILR) are innate immune receptors involved in regulating both innate and adaptive immune functions. LILR show more interspecies conservation than the closely related Killer Ig-like receptors, and homologues have been identified in rodents, primates, seals and chickens. The murine equivalents, paired Ig-like receptors (PIR), contain two additional immunoglobulin domains, but show strong sequence and functional similarities to human LILR. The bovine genome was recently sequenced, with preliminary annotations indicating that LILR were present in this species. We therefore sought to identify and characterize novel LILR within the Bos taurus genome, compare these phylogenetically with LILR from other species and determine whether they were expressed in vivo. Twenty six potential bovine LILR were initially identified using BLAST and BLAT software. Phylogenetic analysis constructed using the neighbour-joining method, incorporating pairwise deletion and confidence limits estimated from 1000 replicates using bootstrapping, indicated that 16 of these represent novel bovine LILR. Protein structures defined using protein BLAST predict that the bovine LILR family comprises seven putative inhibitory, four activating and five soluble receptors. Preliminary expression analysis was performed by mapping the predicted sequences with raw data from total transcript sequence generated using Genome Analyzer IIx (Illumina) to provide evidence that all 16 of these receptors are expressed in vivo. The bovine receptor family appears to contain receptors which resemble the six domain rodent PIR as well as the four domain LILR found in other species.

Highlights

Members of the Leukocyte Immunoglobulin-like receptor (LILR) family are potent modulators of immune function
The human LILR family consists of eleven functional genes and two pseudogenes [9,10,11] encoded within the leukocyte receptor complex (LRC) on chromosome 19q13.4 [10,12]
As LILR contain Ig domains, which are found in many other proteins, the data obtained from BLAST were confirmed, and the chromosomal locations were clarified using the BLAST-Like Alignment Tool (BLAT) (UCSC Genome Bioinformatics, USA, http:// genome.ucsc.edu/cgi-bin/hgBlat, [37])

Summary

Introduction

Members of the Leukocyte Immunoglobulin-like receptor (LILR) family are potent modulators of immune function. Through their expression on monocytic cells, LILR can regulate Toll Like Receptor (TLR) activity [1,2] and antigen presenting phenotype [3,4,5,6]. This ability to regulate both innate and adaptive immune functions of antigen presenting cells indicates that LILR play a pivotal role in shaping immune responses. The IgC2 domains within the human LILR family are referred to as D1-D4

Methods

Results

Conclusion