BACKGROUND & AIMS
: Patients with acute liver failure (ALF) have defe
cts in innate
immune responses to microbes (immuneparesis) and ar
e susceptible to sepsis. Cytotoxic T-
lymphocyte associated protein 4 (CTLA4), which inte
racts with the membrane receptor B7
(also called CD80 and CD86), is a negative regulato
r of T-cell activation. We collected T
cells from patients with ALF and investigated wheth
er inhibitory signals downregulate
adaptive immune responses in patients with ALF.
METHODS
: We collected peripheral
blood mononuclear cells from patients with ALF and
controls from September 2013 through
September 2015 (45 patients with ALF, 20 patients w
ith acute-on-chronic liver failure, 15
patients with cirrhosis with no evidence of acute d
ecompensation, 20 patients with septic
shock but no cirrhosis or liver disease, and 20 hea
lthy individuals). Circulating CD4
+
T cells
were isolated and analyzed by flow cytometry. CD4
+
T cells were incubated with antigen, or
agonist to CD3 and dendritic cells, with or without
antibody against CTLA4; T-cell
proliferation and protein expression were quantifie
d. We measured levels of soluble B7
molecules in supernatants of isolated primary hepat
ocytes, hepatic sinusoidal endothelial
cells, and biliary epithelial cells from healthy or
diseased liver tissues. We also measured
levels of soluble B7 serum samples from patients an
d controls, and mice with
acetaminophen-induced liver injury using ELISAs.
RESULTS:
Peripheral blood samples
from patients with ALF had a higher proportion of C
D4
+
CTLA4
+
T cells than controls;
patients with infections had the highest proportion
s. CD4
+
T cells from patients with ALF had
a reduced proliferative response to antigen or CD3
stimulation compared to cells from
controls; incubation of CD4
+
T cells from patients with ALF with an antibody aga
inst CTLA4 increased their proliferative response to antigen a
nd to CD3 stimulation, to the same levels as
cells from controls. CD4
+
T cells from controls upregulated expression of CT
LA4 following
24–48 hrs culture with sera from patients with ALF;
these sera were found to have increased concentrations of soluble B7 compared to sera from
controls. Necrotic human primary
hepatocytes exposed to acetaminophen, but not hepat
ic sinusoidal endothelial cells and
biliary epithelial cells from patients with ALF, se
creted high levels of soluble B7. Sera from
mice with acetaminophen-induced liver injury contai
ned high levels of soluble B7 compared
to sera from mice without liver injury. Plasma exch
ange reduced circulating levels of soluble
B7 in patients with ALF and expression of CTLA4 on
T cells.
Conclusions
: Peripheral CD4
+
T cells from patients with ALF have increased expre
ssion of CTLA4 compared to individuals
without ALF; these cells have a reduced response to
antigen and CD3 stimulation. We found
sera of patients with ALF and from mice with liver
injury to have high concentrations of
soluble B7, which upregulates CTLA4 expression by T
cells and reduces their response to
antigen. Plasma exchange reduces levels of B7 in se
ra from patients with ALF and might be
used to restore antimicrobial responses to patients.