GH, GH receptor, GH secretagogue receptor, and ghrelin expression in humanT cells, B cells, and neutrophils

We examined GH and GH receptor expression in human leukemic cell lines and leukocytes of normal subjects to elucidate the cell types expressing GH and GH receptor, the individual variations of their expressions, their correla tion and the relationships with serum IgG and IGF-I concentrations. In addi tion, the expression of GH secretagogue receptor, which enhances GH secreti on from the anterior pituitary by synthetic GH secretagogues and that of it s endogenous ligand, ghrelin, were also examined in these immune cells. GH expression in human leukemic cell lines was observed mainly in B cell li nes at both the mRNA and protein level [3.8 +/-0.2 pg/10(6) cells in Raji a nd 19.9 +/-3.3 pg/10(6) cells in Daudi vs. negligible in T cell lines (Jurk at and Hut-78) and in myeloid cell lines (K-562 and RL-60)]. B cells in nor mal subjects were also found to be the major immune cells expressing GH mRN A, with significant individual variation. GH receptor mRNA expression was d etectable in all human leukemic cell lines, although the expression level v aried widely among the cell lines and was weaker than that in the liver. On the other hand, GH receptor mRNA expression was mainly found in B cells, w ith marked individual variation in normal subjects. There was a positive co rrelation between the mRNA expressions of GH and GH receptor in B cells of normal subjects (r=0.89; P<0.001). Single cell RT-PCR revealed that some B cells expressed both GH and GH receptor transcripts, and others expressed o nly GH. GH/GH receptor expression levels in B cells did not show any correl ation with serum IgG and TGF-I levels in normal subjects. Expression of GIT secretagogue receptor and ghrelin was detectable in all immune cells regar dless of the maturity and cell types with great individual variations. In s ummary, GH secreted from B cells may act locally on their own receptors, an d their variable expressions may be related to individual immune functions. Widespread distribution of ghrelin and GH secretagogue receptor in human i mmune cells may indicate unknown biological functions other than enhancing GH secretion in the immune system.