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3
Immune Dysregulation and T-Cell
Activation Antigens in HIV Infection
Mara Biasin, Fulvia Colombo, Stefania Piconi,* and Mario Clerici
Cattedra di Immunologia, Universita' degli Studi di Milano, DISP LITA
Vialba, Milano, Italy, and * I
a
Divisione di Malattie Infettive, Ospedale L.
Sacco, Milano, Italy
INTRODUCTION
Human immunode®ciency virus ( HIV ) infection is associated with a complex
pattern of alterations that profoundly a¨ect the immune response (Cohen et al.,
1997; Levy, 1983; Shearer, 1998). HIV-induced immune dysregulation impairs
both the quantitative and qualitative homeostasis of the immune system, and
this impairment is manifested as an array of multiple, characteristic defects that
can be summarized as follows:
.
A progressive decline in CD4
T-lymphocyte numbers and a profound
impairment of the functionality of these cells
.
A decrease in interleukin (IL)-2, IL-12, IL-15, and interferon ( IFN )g (type-
1 cytokines that mainly stimulate cell-mediated immunity and immune de-
fenses against intracellular pathogens) and an increase in IL-4, IL-5, IL-6,
and IL-10 production (type-2 cytokines that mainly stimulate antibody
production and humoral immunity and are ®nalized at the activation of
immune defenses against extracellular pathogens)
.
Changes in immunophenotype of HIV-infected cells (Table 3.1):
± CD4
T cells increase in the subpopulations expressing CD45RO, Fas
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