Identification, cloning, and characterization of a novel rat natural killer receptor, RNKP30: a molecule expressed in liver allografts.

BACKGROUND

As a component of the innate immune system, natural killer (NK) cells may play a significant role in the early events after solid-organ transplantation. Activated NK cells have been shown to infiltrate allografts in transplant models. To better understand NK cells and the role of NK cell receptors in transplantation, we have cloned and begun characterizing a novel rat molecule, rNKp30.

METHODS

RNKp30 cDNA was cloned by 5' rapid amplification of cDNA ends polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR from mononuclear cells infiltrating a rejecting liver allograft. Southern blot analysis was used to determine the rNKp30 gene copy number. RT-PCR and Northern blotting were used to examine rNKp30 RNA expression in NK cells, multiple tissues, and liver grafts. Immunocytochemistry, immunoprecipitation, and Western blot analysis with two anti-rNKp30 polyclonal antibodies, CA680 and CA1071, were performed. Tunicamycin and endoglycosidase treatments determined the extent of rNKp30 glycosylation.

RESULTS

RNKp30 is homologous to human and macaque NKp30. It is a single copy gene with five identified single-nucleotide polymorphisms. RNKp30 is expressed by NK cells and is detectable as a single transcript by Northern blot in normal spleen, lymph node, and lung tissues. RNKp30 is a variably N-glycosylated cell surface molecule with a protein backbone of approximately 21 kDa. Elevated transcript expression of rNKp30 is detected in both rejected and spontaneously accepted liver allografts, but not in syngeneic or cyclosporine A-treated allografts.

CONCLUSIONS

RNKp30 is a glycosylated surface NK cell receptor with limited polymorphism. This putative activation receptor is expressed in liver allografts and may participate in the innate immune response after transplantation.