title: Effect of recombinant human interferon-alpha in vitro and in vivo on mitogen-induced lymphocyte blastogenesis in cats.
abstract: The effect of recombinant human interferon-alpha (rHuIFN-alpha) in vitro and in vivo on mitogen-induced lymphocyte blastogenesis was evaluated in specific-pathogen-free cats. Pre-incubation of isolated feline peripheral blood lymphocytes (PBL) in vitro with either 10(4) or 10(3) International Units (U) of rHuIFN-alpha for 24 h significantly suppressed (P less than 0.001 and 0.01, respectively) blastogenic responses to the phytomitogens concanavalin A (Con A) and pokeweed mitogen (PWM). Lower doses of IFN (range, 10-10(-3) U/ml) neither suppressed nor enhanced mitogenesis. In the absence of phytomitogens, incubation of PBL with 10(4) - 10(2) U (P less than 0.001) or 10 U (P less than 0.05) of rHuIFN-alpha/ml resulted in a significant decrease in incorporation of [methyl-3H] thymidine into newly synthesized cellular DNA. Cultures of PBL exposed continuously for 4 days to rHuIFN-alpha doses of 10(4) U/ml or less did not demonstrate specific reductions in cell viability, indicating that the observed antiproliferative actions of IFN apparently were independent of any direct cytotoxic effects. To investigate the dose-response effects of rHuIFN-alpha in vivo on lymphocyte blastogenesis, individual groups of cats were evaluated on 3 consecutive days before and then 24 h after each cat was inoculated intramuscularly with either a high dose (10(6) U/kg), moderate dose (10(4) U/kg), or a relatively low dose (10(2) U/kg) of rHuIFN-alpha. Cats inoculated with 10(6) U of rHuIFN-alpha/kg had significantly reduced (P = 0.037) blastogenic responses to Con a at 24 h postinoculation compared to preinoculation values; mean PWM responses were also decreased, but this effect was not statistically significant. In contrast, inoculation of cats with either 10(4) or 10(2) U of rHuIFN-alpha/kg significantly enhanced (P = 0.05 or 0.008, respectively) Con A-induced blastogenesis and had no discernible effect on PWM responses. These findings suggest that very high doses of rHuIFN-alpha given parenterally may be associated with suppression of certain T-cell responses in cats; conversely, much lower doses may be immunoenhancing.
authors: Scott-Ritchey Research Program, College of Veterinary Medicine, Auburn University, AL 36849.
authors: R C
authors: RC
authors: Weiss
authors: T
authors: T
authors: Oostrom-Ram
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002415:Cats / Q000276:immunology*; D002470:Cell Survival; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology; D004261:DNA Replication / Q000187:drug effects; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular / Q000662:veterinary; D007370:Interferon Type I / Q000008:administration & dosage / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology*; D008297:Male; D011043:Pokeweed Mitogens / Q000494:pharmacology; D011897:Random Allocation; D011994:Recombinant Proteins; D013047:Specific Pathogen-Free Organisms
chemical_list: D007370:Interferon Type I; D011043:Pokeweed Mitogens; D011994:Recombinant Proteins; D003208:Concanavalin A