Characteristics of bursal T lymphocytes induced by infectious bursal disease virus.
Infectious bursal disease virus (IBDV) is an avian lymphotropic virus that causes immunosuppression. When specific-pathogen-free chickens were exposed to a pathogenic strain of IBDV (IM), the virus rapidly destroyed B cells in the bursa of Fabricius. Extensive viral replication was accompanied by an infiltration of T cells in the bursa. We studied the characteristics of intrabursal T lymphocytes in IBDV-infected chickens and examined whether T cells were involved in virus clearance. Flow cytometric analysis of single-cell suspensions of the bursal tissue revealed that T cells were first detectable at 4 days postinoculation (p.i.). At 7 days p.i., 65% of bursal cells were T cells and 7% were B cells. After virus infection, the numbers of bursal T cells expressing activation markers Ia and CD25 were significantly increased (P<0.03). In addition, IBDV-induced bursal T cells produced elevated levels of interleukin-6-like factor and nitric oxide-inducing factor in vitro. Spleen and bursal cells of IBDV-infected chickens had upregulated gamma interferon gene expression in comparison with virus-free chickens. In IBDV-infected chickens, bursal T cells proliferated in vitro upon stimulation with purified IBDV in a dose-dependent manner (P<0.02), whereas virus-specific T-cell expansion was not detected in the spleen. Cyclosporin A treatment, which reduced the number of circulating T cells and compromised T-cell mitogenesis, increased viral burden in the bursae of IBDV-infected chickens. The results suggest that intrabursal T cells and T-cell-mediated responses may be important in viral clearance and promoting recovery from infection.
Kim
I J
IJ
Department of Veterinary PathoBiology, University of Minnesota, St. Paul, Minnesota 55108, USA.
You
S K
SK
Kim
H
H
Yeh
H Y
HY
Sharma
J M
JM
D000818:Animals; D018175:Birnaviridae Infections / Q000276:immunology*; D002060:Bursa of Fabricius / Q000276:immunology* / Q000473:pathology / Q000821:virology; D002642:Chick Embryo; D007243:Infectious bursal disease virus; D008213:Lymphocyte Activation; D018655:Lymphocyte Count; D013601:T-Lymphocytes / Q000276:immunology* / Q000821:virology