Objective—To determine the effects of moderate
feed restriction, single or twin pregnancy, and subclinical
pregnancy toxemia (PT) on immune responses
Animals—16 Sardinian ewes.
Procedure—Six weeks before lambing, ewes were
assigned to 1 of 2 groups (n = 8/group) matched for
number of fetuses, body condition score, and plasma
glucose, non-esterified fatty acids (NEFA), and β-
hydroxybutyrate (BHBA) concentrations, and feed
intake was restricted for 1 of the groups. Cell-mediated
immunity was evaluated in vivo and in vitro.
Humoral immunity was evaluated in vivo by determining
production of IgG antibodies against keyhole
limpet hemocyanin (KLH).
Results—Four ewes developed subclinical PT (plasma
BHBA concentration > 0.86 mmol/L without any
clinical signs of disease). Whether feed was restricted
and type of pregnancy (single vs twin) did not have
any significant effects on cell-mediated and humoral
immune responses. Ewes with subclinical PT had significantly
lower in vitro proliferation of phytohemagglutinin-
stimulated peripheral blood mononuclear
cells and significantly lower values for KLH-specific
IgG than did healthy ewes. Plasma BHBA and NEFA
concentrations were negatively correlated with in
vitro proliferation of peripheral blood mononuclear
cells; plasma NEFA concentration was negatively correlated
with values for KLH-specific IgG.
Conclusions and Clinical Relevance—Results suggest
that subclinical PT may be associated with impairments
in cell-mediated and humoral immune responses
in sheep. Am J Vet Res 2001;62:1020–1024)
Objective—To assess the effects of nonesterified
fatty acids (NEFA) and β-hydroxybutyrate (BHBA) on
functions of mononuclear cells obtained from ewes.
Animals—6 Sardinian ewes.
Procedure—Mononuclear cells were cultured with
concentrations of NEFA (0, 15.6, 31.2, 62.5, 125, 250,
500, 1,000, or 2,000 µmol/L) and BHBA (0, 0.45, 0.9,
1.8, or 3.6 mmol/L). Concentrations of NEFA and
BHBA were intended to mimic those of ketotic or
healthy ewes, and NEFA and BHBA were tested alone
and in combination. Synthesis of DNA was stimulated
by use of concanavalin A (Con A) or pokeweed-mitogen
(PWM). Secretion of IgM was stimulated by use
Results—Synthesis of DNA stimulated by Con A and
PWM was significantly inhibited by high concentrations
of NEFA (≥ 250 µmol/L) or by a combination of
high concentrations of NEFA (≥ 250 µmol/L) and all
concentrations of BHBA (≥ 0.45 mmol/L). In contrast,
DNA synthesis was not inhibited by low concentrations
of NEFA (≤ 125 µmol/L) or by a combination of
low concentrations of NEFA (≤ 125 µmol/L) and the
lowest concentration of BHBA (0.45 mmol/L).
Secretion of IgM was significantly inhibited by all concentrations
of NEFA and by all combinations of NEFA
and BHBA concentrations. When used alone, none of
the concentrations of BHBA inhibited DNA synthesis
or IgM secretion.
Conclusions and Clinical Relevance—Reduced
immunoresponsiveness during ketosis is likely to be
associated with an increase in plasma concentration
of NEFA and not with an increase in plasma concentration
of BHBA. (Am J Vet Res 2002;63:414–418)
Objective—To assess effects on functions of peripheral
blood mononuclear cells (PBMC) obtained from
ewes for each of several fatty acids represented in
ovine plasma at concentrations mimicking those of
ketotic or healthy ewes.
Sample Population—Blood samples obtained from
6 Sardinian ewes.
Procedure—The PBMC were cultured in media that
contained oleic (OA), palmitic (PA), stearic (SA), linoleic
(LA), or palmitoleic (POA) acid at concentrations
similar to those of ketotic or healthy ewes. Synthesis
of DNA was stimulated by use of concanavalin A or
pokeweed mitogen (PWM). Secretion of IgM was
stimulated by use of PWM.
Results—High concentrations (900, 450, and 225
µmol/L) of OA significantly inhibited DNA synthesis
and IgM secretion of PBMC. Conversely, low concentrations
(56 or 28 µmol/L) of OA significantly
enhanced DNA synthesis of PBMC. High concentrations
of PA (600, 300, 150, 75, 37.5, or 18.7 µmol/L)
and SA (300, 150, or 75 µmol/L) significantly inhibited
DNA synthesis of PBMC. High concentrations of PA
(600, 300, 150, 75, 37.5, or 18.7 µmol/L) and SA (300,
150, 75, or 38 µmol/L) also significantly inhibited IgM
secretion of PBMC. None of the concentrations of LA
and POA affected PBMC functions.
Conclusion and Clinical Relevance—Impaired
immunoresponsiveness of ketotic ewes is likely associated
with an increase of plasma concentrations of
OA, PA, or SA and not with that of LA or POA. At
physiologic concentrations, single fatty acids are likely
to participate in modulation of immunoresponsiveness
by exerting suppressive or stimulatory effects
on immune cells. (Am J Vet Res 2002;63:958–962)