Antigen-stimulated apoptotic T-cell death in HIV infection is selective for CD4+ T cells, modulated by cytokines and effected by lymphotoxin.
OBJECTIVE
To characterize the mechanism of in vitro antigen-induced apoptotic T-cell death in the peripheral blood mononuclear cells (PBMC) of HIV-1-infected individuals.


METHODS
PBMC from HIV-1 infected and uninfected individuals were unstimulated or stimulated with HIV-1 envelope synthetic peptides (Env) or influenza A virus to determine the extent of antigen-stimulated apoptotic T-cell death, whether this death was limited to the CD4+ subset, and the effects of cytokines on T-cell death. Death was assessed by apoptotic nuclear morphology after 7 days of culture by fluorescence microscopy using a DNA-specific dye. Transwell cultures and supernatant transfers were utilized to test whether a soluble factor produced by HIV-positive PBMC induced death of HIV-negative T cells. Exogenous cytokines [interleukin (IL)-12, interferon (IFN)-gamma, IL-4 and IL-10], as well as antibodies against endogenously produced cytokines (IL-4, IL-10, IL-12, and lymphotoxin) were tested for their ability to modulate death.


RESULTS
Antigenic stimulation induced death in PBMC from HIV-positive donors, but not in PBMC from HIV-negative donors. Antigen-stimulated death was seen in CD4+ but not CD8+ T-cell subset from the HIV-positive patients. Apoptotic death was blocked by IL-12, IFN-gamma, anti-IL-4, anti-IL-10, and anti-lymphotoxin, but not by anti-IL-12. Transwell and supernatant transfer experiment indicated that antigen-stimulated HIV-positive PBMC produced a factor that killed T-cell blasts. The factor was inhibited by anti-lymphotoxin, but not by anti-IL-10.


CONCLUSIONS
Stimulation of HIV-positive PBMC with CD4-dependent antigens results in selective death of CD4+ T cells that is modulated by cytokines. Our results suggest that apoptotic death is not limited to HIV-infected or HIV-specific T cells, but occurs in bystander cells. Lymphotoxin is a mediator of antigen-stimulated T-cell death in this in vitro model.
Clerici
M
M
Cattedra di Immunologia, Universitá degli Studi di Milano, Italy.
Sarin
A
A
Berzofsky
J A
JA
Landay
A L
AL
Kessler
H A
HA
Hashemi
F
F
Hendrix
C W
CW
Blatt
S P
SP
Rusnak
J
J
Dolan
M J
MJ
Coffman
R L
RL
Henkart
P A
PA
Shearer
G M
GM
D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000473:pathology*; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology; D015488:HIV Antigens / Q000276:immunology*; D015658:HIV Infections / Q000276:immunology* / Q000473:pathology; D006801:Humans; D008233:Lymphotoxin-alpha / Q000276:immunology
D000906:Antibodies; D016207:Cytokines; D015488:HIV Antigens; D008233:Lymphotoxin-alpha