Induction of type 2 cytokines by a staphylococcal enterotoxin superantigen.
Persistent intramammary infections of dairy cows with Staphylococcus aureus may involve immunosuppression mediated by bacterial toxins such as enterotoxins and other super-antigens (SAgs). Previously we found that stimulation of bovine PBMC with staphylococcal enterotoxin C (SEC) induced a unique phenotype of activated CD8+ T cells expressing a newly identified activation molecule, ACT3. In the present study we found that SEC induced the expression of interleukin (IL)-4 and IL-10 mRNAs, two cytokines associated with type 2 responses. Elevated levels of IL-4 and IL-10, observed between day 0 and day 4 of culture, were associated with temporary inhibition of proliferative responses of T cells, evidenced by a decrease in numbers of CD4+ T cells and a small increase in numbers of CD8+ T cells. Vigorous proliferation of T cells occurred between days 4 and 7 of culture and with a bias towards CD8+ T cells. Acquisition of the ACT3+ phenotype by CD8+ T cells was preceded by induction of IL-4 mRNA. Thus, in the bovine system, SAgs may hinder protective responses by inducing type 2 cytokines, which interfere with immune clearance of many microbial pathogens. The results of the study are consistent with the hypothesis that SAgs are involved in immunosuppression, and suggest possible immunomodulatory mechanisms.
Ferens
W A
WA
Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow 83844, USA.
Goff
W L
WL
Davis
W C
WC
Fox
L K
LK
Deobald
C
C
Hamilton
M J
MJ
Bohach
G A
GA
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002417:Cattle; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D004768:Enterotoxins / Q000633:toxicity*; D005260:Female; D016753:Interleukin-10 / Q000096:biosynthesis* / Q000276:immunology; D015847:Interleukin-4 / Q000096:biosynthesis* / Q000276:immunology; D008414:Mastitis, Bovine / Q000209:etiology / Q000276:immunology; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D013203:Staphylococcal Infections / Q000209:etiology / Q000276:immunology; D013211:Staphylococcus aureus / Q000276:immunology*; D018089:Superantigens / Q000633:toxicity*
D004768:Enterotoxins; D012333:RNA, Messenger; D018089:Superantigens; D016753:Interleukin-10; D015847:Interleukin-4; C034959:enterotoxin C, staphylococcal