Apoptotic DNA Alterations in Pig Leukocytes After
Phagocytosis of Bacteria are Linked to Maturation of the Immune
System
E. MATALOVÁ1, A. ŠPANOVÁ2,
F. KOVÁŘŮ3
1Institute of Animal Physiology and Genetics, Academy of Sciences,
2Institute of Microbiology, Faculty of Science, Masaryk University
and 3Institute of Physiology, Veterinary and Pharmaceutical
University, Brno, Czech Republic
Received March 19, 2002
Accepted June 14, 2002
Summary
The effect of phagocytosis of living bacteria on apoptotic DNA
changes was examined in pig leukocytes in relation to immune
system maturation. Blood samples of pigs (aged 6, 12 and 18
weeks) were cultivated with a suspension of bacterial cells
Salmonella typhimurium LB 5000 at 37 C. In the experimental
groups, killed bacteria and microspheric particles were used to
detect the influence of the phagocytic process. Phagocytic
activity and index were determined in each sample by means of
microspheric particles. The ability to kill engulfed microbes
(bactericidal capacity) was estimated from the decrease in
bacterial colony-forming units (CFU). Samples of cultured cells
were taken for DNA analysis at given intervals. DNA ladder assay
was used for qualitative apoptotic DNA break detection and the
TUNEL AP test was employed for quantification of apoptosis. In
18-week-old animals, spontaneous DNA degradation was observed in
the control group without phagocytosis after 8 h. In contrast,
cells cultivated with microspheric particles or killed bacteria
became apoptotic after 4 h. The rate of apoptotic DNA
degradation was decreased in the group exposed to living
bacteria. This prolonged survival of phagocytes was also
detected in 12-week-old animals, but not at 6 weeks of age.
These findings were supported by the ability of phagocytes in
6-week-old animals to engulf microbes, but their killing
(bactericidal) ability was significantly decreased in comparison
with other stages of immune system maturation. These results
suggest that the process of phagocytosis itself is accompanied
by activation of the apoptotic program in phagocytic cells of
the pig immune system, but the presence of phagocyted living
bacteria can delay this activation. The prolonged survival of
short-lived cells was only observed in later phases of immune
system maturation.
Key
words
Apoptosis • Phagocytosis • Ontogenesis • Pig leukocytes
Reprint
requests
Eva Matalová, Laboratory of Embryology and Genetics, Institute
of Animal Physiology and Genetics, Academy of Sciences of the
Czech Republic, Veveří 97, 602 00 Brno, Czech Republic. FAX:
+420-5-49211482, E-mail:
matalova@iach.cz.
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