This ppt contain information how the pathogen interact with the host and how the host respond to pathogen

1. HOST RESPONSE TO
BACTERIAL DISEASES
Presented by:
M. Mudassar SU92-MSMBW-S23-003

2. HOST RESPONSE…
• Pathogenic bacteria enter the body through wounds
and skin cuts, often resistant to phagocytes or killer
cells.
o When coated with antibodies, they form a bridge between
bacteria and phagocytes, eliminating extracellular bacteria
through antibody-mediated defense.
o CMI plays a crucial role in extracellular bacteria, while IgA
interferes with attachment molecules.
o Antibodies, acquired through immunization, infection, or
passive neutralization, can interfere with bacteria's normal
function. The protective effect depends on antibodies being
present in body fluids. Circulating helper T cells recognize
these bacterial fragments and produce cytokines

3. Host Response to Bacterial Disease
• It Involves detecting, combating, and resolving infections
caused by bacterial pathogens.
• Innate immune cells include macrophages, dendritic cells,
neutrophils, and natural killer cells, are at the forefront.
• Pathogen-associated molecular patterns (PAMPs) recognize
through pattern recognition receptors.
• Upon bacterial invasion detection, initiate phagocytosis,
produce inflammatory cytokines, and recruit other immune cells.
Immunity involves resistance to infection through the recognition
and disposal of non-self or foreign material.

4. Innate immunity is a
nonspecific host defense against
invading bacteria, influenced by
genetics.
Adaptive immunity, also known
as acquired immunity, is
mediated by B cells or T cells. It
recognizes antigenic molecules
and produces cytokines against
them.

5. • Active or passive immunity results from exposure to an antigen, resulting
in natural infection, vaccination, or passive immunity. It transfers immune
components from an exposed individual to an individual without immunity.
• Super antigens (SAgs) cause excessive
activation of the immune system,
leading to polyclonal T cell activation
and massive cytokine release.
• Cytokines produced by a broad range of
cells, have profound effects on
lymphocyte proliferation and terminal
differentiation.

6. Continue…
• Excessive activation of the immune system, causing non-specific T-
cell activation and massive cytokine release.
• T-cells have specific TCRs on the surface with binding sites
extending to the outside.
• Two major types: helper T (CD4+) and cytotoxic (CD8+) T-cells.
• Roles of T-cells Recognition of peptide epitopes presented by MHC
molecules.
• Activation and clonal expansion of T-cells in case of epitopes
associated with class 11 MHC molecules.
• Production of cytokines that mediate the activation and modulation
of various aspects of the immune response and nonspecific host
defenses.

7. • CD4+ Helper T Lymphocytes Stimulated by antigen in the context of MHC class 11
presentation.
• CD8+ Cytotoxic T-Lymphocytes Lethal to cells expressing the epitope against which
they are directed when presented by class 1 MHC molecules.
Displace virally infected cells through a complement-like action mediated by
perforins and entry of enzymes activating apoptosis.

8. Host Response to Bacterial Disease
• Macrophages: Large Eaters
• Long-lived phagocytes that scavenge dust particles,
microorganisms, and debris.
• Attachment of antigens to macrophages is specific, with specific
receptors for C3 component of complement and Fc component of
antibody.
• They produce and secrete substances such as complement system
components, hydrolytic enzymes, toxic forms of oxygen, and
monoclines.
• • Chronic inflammation is controlled by macrophages, and chronic
inflammation can turn into a granuloma if not cleared.

10. Continue…
Neutrophils: Migration and Inflammatory Signaling
• Neutrophils migrate into tissue only when there is inflammation.
• Macrophages recruit neutrophils to the site of infection, mediating
selectins and adhesions.
• Inflammatory signaling mediators produced by macrophages and
neutrophils include Prostaglandins, lipid derivatives of arachidonic acid,
and Leukotrienes.
Mast Cells and Basophils Cells:
• Concentrated within the respiratory and gastrointestinal tract, and deep
layers of skin.
• Influenced by TH2, IL-13, and IL-4.
• Reside in sub-mucosa, skin, and connective tissue.
• Mast cell proteolytic enzymes tryptase and chymotrypsin increase mucus
production, smooth muscle contraction, and inflammation.

11. Immunoglobulins and Their Role in Immune
Response
• Granulocytes, a type of granulocyte, contain hydrolytic enzymes and
are primary defense against helminth infections.
• Eosinophils contain toxic substances in granules, influenced by IL-3
and IL-5.
• Leukotrienes produced by mast cells can provoke bronchospasm.
• Cationic protein damages the worm's nervous system and can damage
the worm's nervous system.
Neutralizing Antibodies:
• Immunoglobulins (Abs), produced by plasma cells and white blood
cells, can produce a specific immune response.
• IgG is the dominant class of Igs, formed by two light chains and two
heavy chains.

12. • IgA is found in serous and mucus
secretions of respiratory, GI, and urinary
tracts, and neutralizes local toxicities.
• IgM is the largest immunoglobulins,
synthesized in the fetal life and is the most
primitive type of Ig.
• IgM detection in the newborn is a useful
indicator of recent infection and
intrauterine infections.

13. IgD:
• Larger than IgG, with 2 light chains of Kappa (K) useful or Lambda.
• Limited in blood serum, half-life is 2-3 days.
• Has 2 subclasses - IgD1 and IgD2.
• Found associated with B-lymphocytes to act as an antigen receptor.
IgE:
• Two light and 2 heavy chains.
• Low levels in plasma, but 50-100
times higher in allergy individuals.
• High levels noted in helminths
infections.
• Attracts mast cells and basophils
containing K.
• Originally called "REAGIN".

14. Host response….
•
Bacterial Escape Mechanisms:
• Bacteria use various escape mechanisms to evade host immune reaction.
• Some phagocytic bacteria produce chemicals that block phagocyte binding,
leading to inflammatory reactions.
Inflammatory Response in Tissue Injuries:
• Inflammation begins with local arterioles and capillaries, edema fluid
accumulates, fibrin forms a network, and polymorph nuclear leukocytes
migrate towards the irritant.
• Phages engulf microorganisms and initiate intracellular digestion.
• Large macrophages engulf leukocyte debris and microorganisms, paving the
way for resolution of the local inflammatory process.

15. Conclusion
• Inherent and adaptive immunity.
• Cell-mediated immunity uses various cells like WBC,
Macrophage, Phagocytes, Dendritic cells, and T cells.
• Humoral immunity involves B cells, memory cells, and
antibodies.
• Immune response involves cell and immune players
identifying foreign substances, presenting them to the immune
system, and killing/removing them.
• Animal-based bioactive molecules are clinically tested for
antiphrastic, antimicrobial, anti-inflammatory, clot buster, and
antiviral purposes.
• Classic examples include clot-dissolving enzyme, peptides,
and proteolytic enzyme.