1. Department of Microbiology
Cells of Immune system
Department of Microbiology

4. Immune system
Myeloid cells
Granulocytic
Eosinophils
Basophils
Neutrophils
Monocytic
Dendritic cells
Kupffer cells
Macrophages
Lymphoid cells
T cells
Cytotoxic cells
Suppressor cells
Helper cells
B cells
Plasma cells
NK cells

5. Monocytes/Macrophages
Bacteria
Viruses Fungi
Parasites, etc
Pathogens
Immune response
Adaptive immunity
Innate immunity
Neutrophils
Monocytes/Macrophages
Dendritic cells
Natural killer cells
Interferons
Interleukins
Cytokines
Chemokines
Reactive oxygen
substances
T lymphocytes
CD4+
CD8+
Regulatory T cells
Humoral
Cellular
B lymphocytes
antibodies
Pathogen elimination

6. Cells of Innate Immune System
Phagocytes
PMNs/neutrophils
Monocytes/macrophages
NK cells
Basophils and mast cells
Eosinophils
Platelets

7. Neutrophils Most abundant type of white blood corpuscles in mammals.
Characteristic polymorphic nucleus and cytoplasm
Neutrophils are phagocytic cells.
During the beginning (acute) phase of inflammation, particularly as a result of bacterial infection, neutrophils are one of the first to migrate towards the site of inflammation.
Thus, forms first line of defense.

8. Macrophages Literally, “large eaters.”
These are large, long-lived phagocytes which capture foreign cells, digest them, and present / manifest protein fragments (peptides) on their exterior.
In this manner, they present the antigens to the T cells.
Macrophages are strategically located in lymphoid tissues, connective tissues and body cavities, where they are likely to encounter antigens.
They also act as effector cells in cell-mediated immunity.

9. Alveolar macrophages : lung
Histiocytes : connective tissues
Kupffer cells :liver
Mesangial cells :kidney
Microglial cells :brain
Osteoclasts : bone

11. NK cells
T lymphocytes which do not have/ bear either CD 4 or CD 8 markers are called NK cells.
Also known as large granular lymphocytes (LGL).
Kill virus-infected or transformed cells.
Identified by the CD56+/CD16+/CD3-
Activated by IL-2 and IFN-γ to become lymphokine activated killer (LAK) cells.

12. Eosinophils Have characteristic bi-lobed nucleus.
Cytoplasmic granules, stain with acidic dyes (eosin), contains
Major basic protein (MBP)
Potent toxin for helminths
Kill parasitic worms

13. Mast Cell
Large number of mast cells are present within the respiratory and gastrointestinal tracts, and within the deep layers of the skin.
These cells release histamine upon encountering certain antigens, thereby triggering an allergic reaction.
Role in immunity against parasites

14. Process of Phagocytosis

16. Cells of Adaptive Immune Response

17. Cells of adaptive immune response
Lymphocytes
B cells
Plasma cells (Ab producing)
B-memory Cells
T cells
Cytotoxic (CTL)
Helper (Th)
Th1
Th2

18. Lymphocytes
Mature lymphocytes are small cells with a large nucleus and scanty cytoplasm.
There are two broad sub-types of lymphocyte known as B cells and T cells.
All of them are derived from the bone marrow.
In most of the mammals, B cells mature in Bone marrow itself whereas T cells undergo a process of maturation in the thymus .
B and T cells circulate in the blood and through body tissues.

19. Lymphocyte Classes

20. Lymphocytes
B cells give rise to PLASMA CELLS which secrete immunoglobulins (antibodies). Thus, responsible for humoral immunity.
T cells take part in cell mediated immunity.
However, a sub-population of T cells called T helper cells (CD4+) cells secrete cytokines and thereby help in both cellular and humoral immune responses.
CD8+ T cells are cytotoxic cells and main mediator of cell mediated immune response (CMI).
CD8+ cells are able to cause lysis of infected cells.

21. B-Cells B cells are produced in bone marrow.
In most of the mammals, they also mature and acquire immune competence in Bone marrow itself.
In mammals like ruminants, B cells mature in Peyer’s patches and in birds they mature in “Bursa of Fabricius” (Hence the name “B cells).
A mature B cells bear IgM and IgD antibodies on their surface which act as B cell receptors (BCRs).
All the antibody molecule present on the surface of B cells have single specificity i.e., specificity for any single epitope.
Upon maturity, B cells keep on circulating throughout the blood and lymph looking for antigens.

22. B-Cells
Once a B cell has identified an antigen / epiotope, it starts replicating (Clonal selection theory).
The B cells produced in response to antigen stimulation will finally differentiates into two types:
a) Plasma Cells
b) Memory Cells
Plasma cells: Specialized B cells which produce antibodies—more than two thousand per second.
Memory cells: Some of the B cells differentiates into Memory cells. Memory cells are long-lived cells which are capable of mounting immediate response when they encounter same antigen again.

23. B and T cell clones contain lymphocytes that develop into:
Antigen exposure activates only T and B cells with receptors that recognize specific epitopes on that antigen
B and T cell clones contain lymphocytes that develop into:
Effector cells that which target pathogens
Memory cells are long-lived B and T cells
They are capable of division on short notice

24. B lymphocytes Make Antibodies and Memory B cells

25. T-cells
Unlike B cells, these cells leave the marrow at an early age and travel to the thymus, where they mature.
During maturation T cells acquire T- cell receptors in thymus.
The acquisition / generation of T cell receptors is a random phenomenon. Thus, these T cells receptors can recognize all sorts of antigen molecules.
Here in thymus, T cells binding to the “self antigens” undergo “Negative selection” and eventually die.
Thus, only those T cells that do not bind to self antigens are released in the circulation. This forms the basis of self –non self recognition.

26. T-cells
T cells have two important sub populations called helper T cells (CD4+) and cytotoxic (or killer) T cells (CD8+).
These cells travel through the blood and lymph, looking for antigens (such as those captured by antigen-presenting cells).
It is interesting to note that T cells can recognize any antigen / epitope only when they are presented in association with “MHC molecule.”
T helper cells: These CD 4 + cells secretes cytokines which help both B and T cells to mount humoral and cellular immune response, respectively. T helper cells recognize antigen only in association with MHC II molecule.
T cytotoxic cells: These CD 8+ cells kill the cells exhibiting non self antigen on their surfaces in association with MHC I molecule.

28. Antigen Presenting Cells
Cells that link the innate and adaptive arms
Antigen presenting cells (APCs)
Macrophages, Dendritic cells and B cells are considered as professional antigen presenting cells.
They expression MHC class II molecules.
In association with MHC II molecules APCs present antigenic peptides to T helper cells (CD 4+ cells).
T helper cells help in mounting both cell mediated and humoral immune response by adaptive arm.

29. Antigen presentation and T cell activation
Adaptive immunity
Antigen presentation and T cell activation
IFNg
IL- 2
Th1
CD8+
MHC Class I
Naïve Th0
CD4+
Co-stimulatory
signals
MHC Class II
CD80, CD86
Monocytes
Dendritic cells
Microbes
Viral products
Cytokines
Etc.
T cells
APC
Adaptive immune responses involve antigen-specific T-cell proliferation, immunological memory, B cell activation and production of immune antibodies that are all components of an efficient anti-microbial host defense for pathogen elimination and/or protection of the host from future infections. However, this complex process of host immunity can be severely disturbed by the modulating effects of alcohol on the different cellular components of the innate and/or adaptive immune system.
Medzhitov R, Janeway CA Jr. (1997) Innate immunity: impact on the adaptive immune response. Curr Opin Immunol 9:4-9
Th2
IL-10
IL- 4
IL-12, IL-18,
IL-6, IL-8,
TNF-a,
IL-10

30. Antigen presentation and T cell activation
Adaptive immunity
Antigen presentation and T cell activation
IL-12,
IL-10
Antigen-specific T cell proliferation
Th1
Naïve Th0
CD4+
Co-stimulatory
signals
MHC Class II
CD80, CD86
APC
Microbes
Viral products
Cytokines
Etc.
Th2
Naïve Th0
CD4+
Co-stimulatory
signals
MHC Class II
CD80, CD86
APC
Low IL-12,
High IL-10
T cell anergy
Overview of the signals necessary for induction of tolerance and immunity. Antigen presentation (signal 1) in the absence of costimulation (signal 2) results in T cell anergy or depletion. Besides effector T cell activation, costimulation is also important for the activation and expansion of different regulatory T cell subsets. Currently, it is assumed that (an) additional signal(s) (signal 3), such as CD40 ligation of DC and/or the production of inflammatory cytokines by DC, is necessary for induction of efficient T cell immunity.
Cools N, Ponsaerts P, Van Tendeloo VF, Berneman ZN.Balancing between immunity and tolerance: an interplay between dendritic cells, regulatory T cells, and effector T cells.J Leukoc Biol Dec;82(6): Review.

31. CD8 Expansion

32. Circulation of Immune cells
Every B and T cells have predetermined specificity.
For mounting immune response, specific B or T cell must come in contact with antigen molecule.
To make it possible cells of immune system keep on circulating through blood and lymph.
Mostly antigen inoculated through IV route is trapped in Spleen while through IM/SC routes are trapped in regional lymph nodes.

33. THANKS

34. Important Markers on lymphocytes
B cell
T-cytotoxic cells
T-helper
Antigen R
BCR (surface Ig)
TCR
CD3 -- +
CD4
CD8
CD19/ CD20
CD40

35. NK cell
Stem cell
Macrophage
Lymphoid
progenitor
Myeloid
T cell
B cell
Plasma Cell
Granulocyte
Monocyte
Mast cell
Dendritic cell
Bone Marrow
Thymus
Tissues
2° Lymphoid