LeRoith D, Yanowski J, Kaldjian EP, Jaffe ES, LeRoith T, Purdue K, Cooper BD, Pyle R, Adler W. The effects of growth hormone and insulin-like growth factor I on the immune system of aged female monkeys.
Endocrinology 1996;
137:1071-9. [PMID:
8603576 DOI:
10.1210/endo.137.3.8603576]
[Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The aging process is associated with a significant reduction in circulating GH and insulin-like growth factor I (IGF-I) levels. During this period, immune function also declines. Rodent data suggest that treatment with recombinant human GH (rhGH) or rhIGF-I enhances immune function in normal adult mice. To determine whether rhGH and/or rhIGF-I treatment could improve immune function in aged female rhesus monkeys, we administered rhIGF-I (120 micrograms/kg x day), rhGH (100 micrograms/kg x day), a combination of therapies, or excipient alone by sc infusion using Alzet pumps over a 7-week period. At 28 days, the pumps were replaced, and the animals were bled and immunized with tetanus toxoid. At the end of the 7-week period, the animals were killed. rhGH and rhIGF-I increased serum GH and IGF-I levels, respectively; rhGH and rhIGF-I in combination induced the highest serum IGF-I levels (906 +/- 261 ng/ml vs. control, 185 +/- 36 ng/ml at death). rhGH and rhIGF-I also increased IGFBP-3 levels. rhGH infusion resulted in the most marked changes in lymph node and splenic reactivity, as determined by histological assessment. Lymph nodes from the rhGH-treated animals showed changes from baseline indicating a stimulated reactive state. Both rhGH and rhIGF-I had effects on lymphocyte phenotype, but there were different responses in blood compared to spleen and lymph nodes. In the peripheral blood, the percent B cells and percent CD8 cell count rose after rhIGF-I therapy, with a fall in the CD4/CD8 ratio. In the spleen, on the other hand, the CD4/CD8 ratio nearly doubled (0.33 +/- 0.12 vs. 0.53 +/ 0.12) after rhIGF- I therapy. In the spleen, the combination of rhGH and rhIGF- I increased the percent T cells from 26.7 +/- 2.3 to 42.4 +/- 4.4 and the CD4/CD8 ration to 0.71 +/- 0.11. Both rhGH and rhIGF-I increased in vivo (antibody titer to tetanus toxoid) responses by lymphocytes, and rhGH increased Con-A- induced DNA synthesis in vitro. These results confirm the rodent data showing that rhGH and rhIGF-I cause beneficial changes in immune function and suggest that further investigation is warranted to assess their therapeutic potential.
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