1. Innate Immunity

4. Cellular Innate Immunity

5. Cells Involved in the Innate Immune System
Polymorphonuclear Leukocytes “PMNLS”, “granulocytes”.
Basophils
Mast cells
Eosinophils
Neutrophils
Monocyte and macrophage
Innate lymphoid cells
Mast cell
Dendritic cell

6. Cells Involved in the Innate Immune System
They contain the enzyme – rich lysosomes.
They produce peroxide and superoxide radicals which are toxic to many microorganisms
Some lysosomes contain bactericidal proteins, such as lactoferrin.
Defects in PMN cell function are accompanied by chronic or recurrent infection
Some of them have a major role in antigen detection and presenting

8. Phagocytes Neutrophils
Neutrophils are produced at a rate of 7 million per minute and released from bone marrow.
They are short –lived “2-3 days”
They represent 95% of the circulating granulocytes.

9. Neutrophils are the first white blood cells recruited to sites of acute inflammation, in response to chemotactic cues such as CXCL8 (interleukin-8, IL-8) produced by stressed tissue cells and tissue-resident immune cells such as macrophages.
Neutrophils therefore comprise a large proportion of the early cellular infiltrate in inflamed tissues and are the major constituent of pus.

11. Other small granules contain gelatinase
They contain antibiotic proteins which are stored in two main types of granules:
1- The primary “azurophilic “ granules, they are lysosomes containing acid hydrolases , myeloperoxidase, lysozyme, defensins and bacterial permeability inducing protein ”BPI”.
2- The secondary granules “ specific to neutrophils” contain lactoferrin and lysozyme.
Other small granules contain gelatinase
Neutrophils can also release granules and cytotoxic substances extracellularly when they are activated by immune complexes through their Fc receptors.

12. Neutrophil under Electron Microscope

13. Macrophages:
They are phagocytes derived from blood monocytes. Have different names:
Kupffer cells, in the liver.
Alveolar macrophages, in the lung.
Splenic macrophages, in the white plup.
Peritoneal macrophages, free floating in peritoneal fluid.
Microglial cells, in the central nervous system.

15. Two main pathways of macrophage: reverse action

16. 10 cl 12 re cancer switching

17. Endocytosis
It is the ingestion of macromolecules present in extra cellular tissue fluid.
This occurs either by nonspecific membrane invagination or by receptor mediated endocytosis with endocytic vesicle – endosome- lysosomes yield breakdown products.

18. Phagocytosis
The ingestion of invading particles e.g. bacteria – by phagocytic cells.
Phagocytosis is aided by opsonins “antibodies, complement components”.
The foreign particle is entrapped in a phagocytic vacuole.

20. Intracellular killing
Oxygen dependent
Myeloperoxidase dependent
H2O2 + O2-
2O2- + 2H+
Superoxide dismutase
H2 O2 + Cl-
myeloperoxidase
OCl- + H2O
H2O + O2-
2 H2 O2
catalase
2OCL- + H2O
1O2-+ Cl-+ H2O

21. Oxygen dependent Oxygen independent 2O2- + H2O2 .OH + OH- + 1O2
Myeloperoxidase independent
Oxygen independent
2O2- + H2O2
.OH + OH- + 1O2
Glucose +NADP+
G-6-P-dehydrogenase
Pentose-P
+ NADPH
NADPH + O2
Cytochrome b558
NADP++ O2-
2O2- + 2H+
Superoxide dismutase
H2O2 + 1O2

24. Innate lymphoid cells (ILCs)
are a group of innate immune cells that belong to the lymphoid lineage but do not respond in an antigen-specific manner, as they lack a B or T cell receptor.
ILCs do not express myeloid or dendritic cell markers.
Classified at the first time in 2013 according to transcriptional factors and cytokine release into three groups :
Group 1 ILCs or ILCs1 :
can produce type 1 cytokines (notably IFNγ and TNF) and comprise NK cells and ILC1s.
analogous to Th1 and cytotoxic T cells (tumor and viral clearance).
ILC1s are weakly cytotoxic cells closely related to ILC3s .
Raise Natural killer ('NK') cells 

25. Group 2 ILCs
Can produce type 2 cytokines (e.g. IL-4, IL-5, IL-9, IL-13).
Also termed natural helper cells, nuocytes, or innate helper 2 cells .
analogous to Th2 cells ( helminthic infection).
Group 3 ILCs
defined by their capacity to produce cytokines IL-17A and/or IL-22 .
Raise Lymphoid tissue inducer ('LTi') cells  essential for development of lymphoid organs during embryogenesis and after birth
analogous to Th17 cells (Enteric pathogens clearance, lymphoid tissue development, memory T cells maintenance)

26. Spits, et al., 2013

28. Dendritic cells
Long lived, reside in an immature state in most tissues
They recognize and phagocytize pathogens and other antigens.
They are found as inter digitating cells of the thymus and Langerhans cells in the skin.
They are derived from the same hematopoietic precursor cells as monocytes.
Direct contact with many pathogens leads to the maturation of dendritic cells and increasing their antigen presenting capacity such maturation allows them to activate naïve antigen specific T-cells. Thus they are important in both innate immunity and the initiation of adaptive immune responses.

30. Natural killer cells :
a lymphocyte able to bind to certain tumour cells and virus-infected cells without the stimulation of antigens, and kill them by the insertion of granules containing perforin
They lack TCRs
NK cells express non – TCR – related receptors called killer cell inhibitory receptors (KIR) which bind to MHC class I molecules.
Killing is achieved by the release of various cytotoxic molecules, some of these cause the pore formation on the membrane of target cells, leading to its lysis, other molecules enter the target cell and cause apoptosis.

31. Functions
Killing infected cells (cytotoxic)
Secretion of cytokines
Activation by
Type 1 interferons
Infected cells
Stimulates cytotoxic function
IL-12 and TNF-alpha
Macrophages
Stimulates cytokine secretion

32. Functions of NK cells

33. 33

34. Differentiate infected from uninfected cells
Activated NK cells release IFN-gamma and IL-12 which activates macrophages
Differentiate infected from uninfected cells
NK cells express receptors for MHC class I molecules
Binding of NK cells to MHC class I molecules turn off NK cells
NK cells provide innate immunity to intracellular pathogens
NK cells vs NKT cells
NKT cells are NOT the same as NK cells.
NKT cells are T cells with an αβ TCR. However, they also express some of the cell-surface molecules of NK cells — hence their name 34

37. Functions of activating and inhibitory receptors of NK cells

38. So how all these cells recognize different antigens??

39. Pattern recognition receptors (PRRs)
The interaction with the pathogen can be direct by pattern recognition receptors (PRRs), or indirect, through recognition of opsonised microbes by Fc receptors or complement receptors.
PRRs play a crucial role in the proper function of the innate immune system.
PRRs are germline-encoded host sensors, which detect molecules typical for the pathogens.
They are proteins expressed, mainly, by cells of the innate immune system, such as dendritic cells, macrophages, monocytes, neutrophils and epithelial cells.

40. Pattern recognition receptors (PRRs)
PRR identify two classes of molecules: 
Pathogen-associated molecular patterns (PAMPs), which are associated with microbial pathogens.
Damage-associated molecular patterns (DAMPs), which are associated with components of host's cells that are released during cell damage or death.
They are also called primitive pattern recognition receptors because they evolved before other parts of the immune system, particularly before adaptive immunity.
PRRs also mediate the initiation of antigen-specific adaptive immune response and release of inflammatory cytokines.

42. PRRs devided into three classes :
Membrane-bound PRRs :
Receptor kinases
Toll-like receptors (TLR)
C-type lectin Receptors (CLR)
Cytoplasmic PRRs : multifunctional ! !
DS viral DNA, gram negative peptedoglycan, apoptosis …
Secreted PRRs :
Complement receptors, collectins (as MBL), pentraxins (as CRP)

43. Toll – like receptors "TLRs":
Each recognizes specific microbial components. Activation of TLRs by microbial components leads to activation of the innate immunity as well as adaptive immunity through production of cytokines and expression of co simulators molecules.
Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single, membrane-spanning, non- catalytic receptors usually expressed on many immune cells to recognize structurally conserved molecules derived from microbes. Once these microbes have reached physical barriers such as the skin or intestinal tract mucosa, they are recognized by TLRs, which activate immune cell responses. The TLRs include TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, TLR11, TLR12, and TLR13, though the latter three are not found in humans.
TLR's received their name from their similarity to the protein coded by the toll gene identified in Drosophila.

45. TLRs: location and target

46. Different TLRs can recognize different antigens as listed below
TLR-1:- Bacterial lipoprotein and peptidoglycans
TLR-2:- Bacterial peptidoglycans
TLR-3:- Double stranded RNA
TLR-4:- Lipopolysaccharides
TLR-5:- Bacterial flagella
TLR-6:- Bacterial lipoprotein
TLR-7:- Single stranded RNA
TLR-8:- Single stranded RNA
TLR-9:- CpG DNA
TLR-10:- Unknown
2-4 neutro
8/10 macro better

48. Recognition of microbes and damaged self by the innate immune system

49. Cellular location of pattern recognition molecules of the innate immune system

50. TLRs are essential for innate cell specificity in infection fighting
TLRs are essential for innate cell specificity in infection fighting. Example: neutrophils have no TLR3 so they are not efficient in fighting dsRNA viruses.

52. Other receptors involved in the Innate Immune system:
F-met-Leu-phe receptor on neutrophils:
A chemotactic receptor that binds the N-formylated peptides of certain bacteria and guides neutrophils to the site of infection
Mannan - binding "MB" lectin:
These enable phagocytes to recognize pathogenic microbe – expressed polysaccharides.
Ligation of the phagocyte MB lectin “receptor” with these sugars initiated and activated the MB lectin pathway of complement.
Scavenger receptors:
Receptors on phagocytes recognize specific anionic polymers expressed by certain pathogens and old dying RBCs, leading to the removal of these cells.

53. Indirect interaction with microbes through recognition of opsonised microbes by Fc receptors or complement receptors

54. Humeral Innate Immunity: the complement system

55. COMPLEMENT SYSTEM It consider as part of innate immune system .
Components that provide activity of blood serum that completes the action of antibody.
The proteins and glycoproteins are synthesized mainly by hepatocytes.
Most circulate in the serum in functionally inactive forms: proenzymes, or zymogen .
They are activated by proteolytic cleavage; which removes an inhibitory fragment and exposes the active site.
Heat-labile component of serum .
The complement system is not adaptable and does not change over the course of an individual's lifetime.
1-Some amounts are produced by monocytes, macrophages, and epithelial cells of the GI and genitourinary tracts

58. KEY COMPONENTS OF THE COMPLEMENT SYSTEM
 Complement components are designated by numerals (C1– C9), by letter symbols (e.g., factor D), or by trivial names (e.g., homologous restriction factor)
Peptide fragments formed by activation of a component are denoted by small letters
In most cases, the smaller fragment resulting is designated “a” and the larger fragment designated “b” • Ex: C3a, C3b •
C2 is an exception: C2a is the larger cleavage fragment
The larger fragments bind to the target near the site of activation
The smaller fragments diffuse from the site and can initiate localized inflammatory responses by binding to specific receptors
Fragments interact with one another to form functional complexes
Complexes that have enzymatic activity are designated by a bar over the number or symbol (e.g., C4b2a, C3bBb)

59. ACTION OF THE COMPLEMENT SYSTEM
The triggering and amplification of inflammatory reactions.
Attraction of phagocytes by chemotaxis
Clearance of immune complexes
Cellular activation
Direct microbial killing
An important role in the development of antibody responses.

61. C1 protein

62. Complement regulation
There are several levels of regulation of the complement system:
First : the specific binding of the C1qr2s2 complex to antigen-bound, cell-bound antibody.
This ensures that complement is not activated by random contacts between soluble antibodies and complement components .
Second regulation relates to the short half life and limited stability of a number of the complement components once they have been produced in their active form.
Thirdly a number of specific regulator proteins exist that block specific steps of the activation pathways or MAC activity.
Finally Fourth, other proteins such as HRF and MIRL (CD59) block the final assembly of the pore by preventing binding of C9. 

63. Note :
The activity of many complement regulatory proteins is species-specific.