Immunity involves both specific and non-specific components of the immune system. The non-specific components act as barriers or eliminate a wide range of pathogens, while the specific components adapt to each new disease and generate pathogen-specific immunity. Cell-mediated immunity is mediated by activated macrophages, natural killer cells, cytotoxic T-lymphocytes, and cytokines and does not involve antibodies. It is responsible for phagocytosing and killing intracellular pathogens and virus-infected cells. Memory T cells provide long-term immunity against past infections upon reexposure to the pathogen.

2. “ Immunity is
Immunity involves both Other components of
basically a biological
specific and non-specific the immune system
term that describes a
components. The non-specific adapt themselves to
state of having
components act either as each new disease
sufficient biological
barriers or as eliminators of encountered and are
defenses to avoid
wide range of pathogens able to generate
infection, disease, or
irrespective of antigenic pathogen-specific
other unwanted
specificity immunity
biological invasion ”

3.  There are 2 types of Immunity
1) Adaptive Immunity
2) Innate Immunity.

4.  Cell-mediated immunity is an immune response
that does not involve antibodies or complement but
rather involves the activation of macrophages, natural
killer cells (NK), antigen-specific cytotoxic T-
lymphocytes, and the release of various cytokines in
response to an antigen.
 The second arm of the immune response is refered to
as Cell Mediated Immunity (CMIR). As the name
implies, the functional "effectors" of this response are
various immune cells.

5. These functions include:
 Phagocytosis and killing of intracellular pathogens
 Direct cell killing by cytotoxic T cells
 Direct cell killing by NK and K cells

6. While the production of antibody through the humoral
immune response can effectively lead to the elimination of
a variety of pathogens, bacteria that have evolved to invade
and multiply within phagocytic cells of the immune
response pose a different threat.
The following will aid in its Explanation :
1) Extracellular microorganisms
 Non-encapsulated microorganisms are easily phagocytosed
and killed within macrophages.
 Encapsulated microorganisms require the production of
antibody in order to be effectively phagocytosed. Once
engulfed, however, they are easily killed.

7. 2) Intracellular microorganisms
 Intracellular microorganisms elicit the production of
antibody, which allows effective phagocytosis. Once
engulfed, however, they survive within the phagocyte
and eventually kill it.
 Intracellular microorganisms also activate specific T-
cells, which then release lymphokines (e.g. IFN, TNF)
that cause macrophage activation. Activated ("killer")
macrophages are then very effective at destroying the
intracellular pathogens.

9. The second half of the cell-mediated immune response
is involved in rejection of foreign grafts and the
elimination of tumors and virus-infected cells. The
effector cells involved in these processes are cytotoxic
T-lymphocytes (CTLs), NK-cells and K-cells. Each of
these effector cells recognizes their target by different
means, described below :
1) Cytotoxic T-lymphocytes:

10.  1) T Helper cells (TH cells)
 2) Cytotoxic cells (Tc cells or CTLs)
 3) Memory T Cells.
 4 Regulatory T cells
 .

11.  1) T helper cell(TH cells) assist other white blood
cells in immunologic processes, including
maturation of B cells into plasma cells and
activation of cytotoxic T cells and
macrophages, among other functions.
 2)Cytotoxic T cells (TC cells, or CTLs) destroy
virally infected cells and tumor cells, and are also
implicated in transplant rejection

12. 3) Memory T cells are a subset of antigen-specific T
cells that persist long-term after an infection has
resolved. They quickly expand to large numbers of
effector T cells upon re-exposure to their cognate
antigen, thus providing the immune system with
"memory" against past infections. Memory T cells
comprise two subtypes: central memory T cells
(TCM cells) and effector memory T cells (TEM cells
Regulator).

13. 4) Regulatory T cells (Treg cells) formerly known as
suppressor T cells, are crucial for the maintenance of
immunological tolerance. Their major role is to shut down
T cell-mediated immunity toward the end of an immune
reaction and to suppress auto-reactive T cells that escaped
the process of negative selection in the thymus.

14.  2) NK(Natural killer) cells:
NK cells are part of a group known as the "large
granular lymphocytes". These cells are generally non-
specific, MHC-unrestricted cells involved primarily in
the elimination of Neoplastic or tumor cells
 The precise mechanism by which they recognize their
target cells is not clear. Probably, there is some type of
NK-determinant expressed by the target cells that is
recognized by an NK-receptor on the NK cell surface.
Once the target cell is recognized, killing occurs in a
manner similar to that produced by the CTL.

15.  3) K-cells:
K-cells are probably not a separate cell type but rather
a separate function of the NK group. K-cells contain
immunoglobulin Fc receptors on their surface and are
involved in a process known as Antibody-dependent
Cell-mediated Cytotoxicity (ADCC). ADCC occurs as a
consequence of antibody being bound to a target cell
surface via specific antigenic determinants expressed
by the target cell. Once bound, the Fc portion of the
immunoglobulin can be recognized by the K-cell.
Killing then ensues by a mechanism similar to that
employed by CTLs. This type of CMIR can also result
in Type II hypersensitivities.

17. Explanation of above Diagram
 Stimulation of immune response by activated
helper T cells activated by complex interaction with
molecules on the surface of a macrophage or some
other antigen-presenting cell, a helper T cell
proliferates into two general subtypes, TH1 and TH2.
These in turn stimulate the complex pathways of the
cell-mediated immune response and the humoral
immune response, respectively.

18.  COMPONENTS AND FUNCTIONS OF THE
COMPLEMENT SYSTEM
 The complement system found in the blood of mammals is
composed of heat labile substances (proteins) that
combine with antibodies or cell surfaces. This complex,
multicomponent system is composed of about 26 proteins.
The "complement cascade" is constitutive and non-specific
but it must be activated in order to function. The functions
of complement include:
 Making bacteria more susceptible to phagocytosis
 Directly lysing some bacteria and foreign cells
 Producing chemotactic substances

19.  Increasing vascular permeability
 Causing smooth muscle contraction promoting mast
cell degranulation .
Hypersensitivity
Hypersensitivity (also called hypersensitivity reaction)
refers to undesirable (damaging, discomfort-
producing and sometimes fatal) reactions produced by
the normal immune system. Hypersensitivity
reactions require a pre-sensitized (immune) state of
the host.

20. It is classified into five different types
1) Allergy
2) CytoToxic Anti-Body dependent
3 )Immune complex Disease
4) Delayed type Hypersensitivity Response
5) Auto-Immune Disease.
Only type IV of Hyper Sensitivity is related to this topic
. . Because its chemical mediators are T-cells

21. Cell-Mediated Immunity
Prepared by : Farrukh Nadeem
Yasir Yaqoob : Talha Ahmed : Arnold Raffique.