Molekularbiologische und funktionelle Charakterisierung neuer "Chicken Ig-like" Rezeptoren

Some recently described receptor families on myeloid and lymphoid
cells in man and mouse have both inhibitory and activating
receptors with important functions in the regulation of the immune
system. Due to the lack of information regarding these receptors in
other vertebrates, in the present thesis seven new members of this
receptor family were identified in the chicken. All receptors
identified were located on one single clone of a chicken BAC
library, which indicates that they are tightly clustered on the
chromosome. This localisation and the high amino acid homology
suggests, that they belong to a multigene-family. Analysis of the
genomic organisation showed, that the signalpeptide was split into
two exons, each Ig-domain and the transmembrane region were encoded
by separate exons and the long cytoplasmic tail (in case of
inhibitory receptors) was encoded by two exons, the last exon
containing the ITIMs. The exon/intron boundaries conformed to the
gt-ag rule and the exon phases were highly conserved. In
conclusion, the genomic organisation showed conserved features of
mammalian Ig-like receptor genes. The novel identified CHIR were
grouped into three different types of receptors. The activating
CHIR-A had two extracytoplasmic Ig-domains and a short cytoplasmic
tail, but a positively charged amino acid in the transmembrane
region, which could associate to an ITAM-containing adaptor
molecule. CHIR-A2 had a relative molecular weight of ~ 42 kDa and
was detected in the mRNA of bursa, spleen, PBL, NK-cells and
different macrophage- and B-cell lines. The inhibitory CHIR-B
consisted of two Ig-domains and a long cytoplasmic tail with two
ITIMs in it. CHIR-B2 had a relative molecular weight of ~ 46 kDa
and was only detectable on B-cells by a newly produced specific
monoclonal antibody (mAb). Upon Pervanadate treatment the ITIMs in
the cytoplasmic tail were phosphorylated and recruited the
protein-tyrosine- phosphatases SHP-1 and -2. Additionally ligation
of CHIR-B2 had an inhibitory effect on the cell proliferation of a
B-cell line. The potentially inhibitory and activating CHIR-AB had
one Ig-domain, a long cytoplasmic tail with one ITIM in it and a
positively charged amino acid in the trans-membrane region, which
could associate with an ITAM-containing adaptor molecule. The only
CHIR-AB homologue in the literature is KIR2DL4, that represents a
highly conserved Ig-like Receptor expressed on all primate NK-cells
with both activating and inhibitory function. CHIR-AB1 had a
molecular weight of ~ 40 kDa and its expression on B-cells, on the
B-cell line DT-40, on primary macrophages, different macrophage
cell lines and on NK-cells in the gut was detected by a specific
mAb.