Decline in the expression of C4 binding protein alpha-chain gene during ageing of the rat liver

It appears that consistent changes in the levels of activity of a small cohort of genes (probably less than 1% of all active genes) occur in all mammalian cells during ageing. We have studied this phenomenon in rat liver using an optimised form of differential display. During this investigation we observed one gene which exhibited a decline in expression in livers from young adult (6 months) to aged adult (24 months) animals. The differential expression of this gene was confirmed by single strand conformational polymorphism (SSCP) gel analysis and Northern blotting. Densitometry of the latter indicated that there was a decline of 35% in its expression with age. Characterisation of the isolated PCR fragment demonstrated it to code for the alpha subchain of the complement 4 binding protein (C4BP). The C4BP is a key regulatory protein of the complement system and this observation therefore indicates that a decline in the efficiency of the complement system may be an important factor in the overall decline in immune function that has been observed during ageing.