Differences in proliferation of the hematopoietic cell line TF-1 and cytokine production by peripheral blood leukocytes induced by 2 naturally occurring forms of human IL-3.
BACKGROUND
A naturally occurring polymorphism in the coding region of the human IL3 gene leads to a change in amino acid residue 8 from proline to serine.


OBJECTIVE
We sought to determine whether the 2 different forms of IL-3 varied in function. These different forms are available as recombinant proteins (recombinant human IL-3/proline 8 [rhIL-3/P8] and recombinant human IL-3/serine 8 [rhIL-3/S8]).


METHODS
The erythroleukemic cell line TF-1 was incubated with varying concentrations of rhIL-3/P8 or rhIL-3/S8 to determine the capacity of each type of IL-3 to induce proliferation. Human leukocytes were primed with rhIL-3/P8 or rhIL-3/S8 for up to 24 hours and then stimulated with anti-IgE and assessed for leukotrienes (LTs), IL-4, and TNF-alpha.


RESULTS
Proliferation of TF-1 cells was induced by both forms of IL-3 at 48 and 72 hours but to a greater degree by rhIL-3/P8. In contrast, the mean fold increase over control values of LT and IL-4 production was higher after priming the cells with rhIL-3/S8 versus rhIL-3/P8. Additionally, TNF-alpha production was greater (and reached significance only) for rhIL-3/S8. This activity was independent of IgE and thus directly stimulated by IL-3. Studies with basophil-enriched and basophil-depleted cell preparations revealed that LT production was evident only from the former and TNF-alpha only from the latter.


CONCLUSIONS
We conclude that the 2 naturally occurring forms of human IL-3 have similar spectra of activities on cells with IL-3 receptors, but the 2 forms have reversed relative efficacies for promoting proliferation (rhIL-3/P8 > rhIL-3/S8) compared with priming or inducing mediator secretion (rhIL-3/S8 > rhIL-3/P8).
Respiratory Sciences Center, The University of Arizona, Tucson, USA.
A
A
Schweiger
D
D
Stern
I C
IC
Lohman
M
M
Baldini
F D
FD
Martinez
M
M
Halonen
D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis* / Q000097:blood; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D007377:Interleukin-3 / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D007962:Leukocytes / Q000187:drug effects*; D011392:Proline / Q000032:analysis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012694:Serine / Q000032:analysis; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016207:Cytokines; D007377:Interleukin-3; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D012694:Serine; D011392:Proline