Introduction to CELL APOPTOSIS Including Definition Micro-organism which cause CELL APOPTOSIS Mechanism by which some bacteria lead to CELL APOPTOSIS Some factors which facilitate microbes to present CELL APOPTOSIS Sequence effects of Cell-Apoptisis

1. CELL APOPTOSIS
A J Zaahir Bsc MLT

2. OUTLINES
 Introduction to CELL APOPTOSIS
 Including Definition
Micro-organism which cause CELL APOPTOSIS
Mechanism by which some bacteria lead to
CELL APOPTOSIS
Some factors which facilitate microbes to
present CELL APOPTOSIS
Sequence effects of Cell-Apoptisis

3. Introduction to CELL APOPTOSIS
CELL DEATH
The morphologic hallmark of cell death is loss of the
nucleus, which occurs via :-
 Pyknosis: condensation of chromatin and shrinkage of
the nucleus.
 Karyorrhexis: fragmentation of the nucleus.
 Karyolysis: dissolution of the nucleus.

4. Cont..

5. Cont….
There are two mechanisms of cell death , which are
Necrosis :- Pathological cell death
and
Apoptosis :- Programmed Cell Death

6. DEFINITION OF CELL- APPOPTOSIS
o Apoptosis is the death of single cells within clusters of
other cells.
o In apoptosis, the cell shows shrinkage & increased
acidophilic staining of the cell ,
 This is followed by fragmentation of the cells.
o Apoptosis usually occurs as a physiologic process for
removal of cells during embryogenesis, menstruation,
etc…

7. Micro-organism which cause CELL APOPTOSIS
Apoptosis usually occurs as a
physiologic process
BUT
 it can also be seen in pathological
conditions caused by mild injurious
agents and pathogenic microbes .

8. Micro-organism which cause CELL
APOPTOSIS Include :-
 viral hepatitis
 Staphylococcus aureus
 Escherichia coli
 Corynebacterium diphtheriae
 Shigella dysenteriae
 ETC

9. Mechanism by which some bacteria lead to CELL
APOPTOSIS
I. Pore Formers vs Host Cells
 A wide range of bacteria produces pore-forming toxins that
interfere with the cell cycle regulation. For instance, these
toxins upset the selective mobilization of ions across the
plasma membrane by introducing a transmembrane pore. Both
gram-positive and gram negative bacteria produce pore-
forming toxins, such as the RTX (repeats in toxin) toxins
produced by certain gram-negative bacteria, streptolysin O by
Streptococcus pyogenes, and the Staphylococcus aureus α-
toxin

10. II.Infection with Protein Synthesis Inhibitors
An assortment of bacterial species is concerned with this
group. These pathogens are responsible for the type of host
cell death that is triggered by protein synthesis inhibition, and
are capable of doing so by the secretion of specific bacterial
proteins (toxins), which have intrinsic enzymatic activity.
These proteins consist of an A-B conformation with the B
subunit being able to mediate ligation with eukaryotic cells
and the enzymatically operational A fragment translocated
across the cell membrane to its cytosolic destination.

11. Cont….
Some of the examples of these proteins are
diphtheria toxin (Dtx) secreted from
Corynebacterium diphtheriae, Pseudomonas
exotoxin A, and the Shiga and Shiga-like toxins

12. factors which facilitate microbes to
present CELL APOPTOSIS
Apoptotic cells are potently
immunosuppressive, eliciting a repertoire of
immunomodulatory responses termed
'innate apoptotic immunity' (IAI).
IAI is triggered upon recognition of protein
determinants externalized on the apoptotic
cell surface, independent of phagocytosis.

13. Cont…
IAI is exploited by pathogens to modulate
host immunity, thereby enhancing their
pathogenicity.
Pathogens use distinct strategies for the
exploitation of IAI. Among these are
apoptotic subversion, apoptotic mimicry,
and death reprogramming

14. Sequence effects of Cell-Apoptisis
The clearance of apoptotic cells is a highly regulated
mechanism, normally associated with anti-
inflammatory response.
During early stages of apoptosis the cell is promptly
recognized and engulfed by professional phagocytes
or tissue cells to avoid the outflow of intracellular
content and limit the immunological reaction against
released antigens

15. Cont…..
However, increasing evidences suggest that impairment in the
uptake of apoptotic cell debris is linked to the development of
autoimmunity .
In a healthy body, the number of cells stays constant. Millions
of new cells are produced every second, and millions of
others are lost or kill themselves.
A failure in apoptosis could lead to cancer - uncontrolled
growth.
Excessive apoptosis could cause wasting away as in
Alzheimer's and Parkinson's diseases