This document provides an overview of immunity, including its types and components. It discusses: 1. Innate immunity, which provides the first line of defense, and adaptive/acquired immunity, which is antigen-specific and provides immunological memory. 2. The cells involved in innate immunity like phagocytes and those involved in adaptive immunity like B and T cells. 3. The types of acquired immunity, including active (natural/artificial) and passive (natural/artificial), and their characteristics and effectors like antibodies versus cell-mediated responses.

1. Department of Microbiology
Srishti Patel
MSc. Final Year ( 3rd sem )

2. IMMUNITY
ITS TYPES
IMMUNITY
Immunity can be defined as a complex biological system endowed ( provided ) with the
capacity to recognize and tolerate whatever belongs to the self, and to recognize and
reject what is foreign (non-self).
TYPES OF IMMUNITY
1. Innate Immunity- The innate immune responses are the first line of defense against
invading pathogens. They are also required to initiate specific adaptive immune
responses.
2. Adaptive/Acquired Immunity- The adaptive immune system, is a subsystem of the
immune system that is composed of specialized, systemic cells and processes that
eliminate pathogens or prevent their growth.

3. CELLS IN INNATE
AND ADAPTIVE
IMMUNE SYSTEM

4. IMMUNITY
ITS TYPES IMMUNITY
PASSIVE
ACTIVE
ACQUIRED
INNATE
SPECIES
RACIAL
INDIVIDUAL

5. INNATE
IMMUNITY
INNATE IMMUNITY
• Also know as Non- Specific Immunity and provides the first line of defense
• Given by genetic makeup
• Generates a fast inflammatory response that is generic to all types of pathogens or tissue
damages and does not confer immune memory to the host.
• initiated within hours and provides a rapid array of defenses
TYPES OF DEFENSES/BARRIERS
1. The anatomical or chemical barriers- these include the skin, mucous membrane, gastro-intestinal
tract, urino-genital tract and respiratory tract that are responsible of preventing the entry of
pathogen or to trap the pathogen during its entry in the body.
2. The phagocytic barriers- these include the leukocytes present in blood that are capable of
performing phagocytosis and killing the pathogen, for example, macrophages, neutrophils, natural
killer cells.
3. Plasma proteins- plasma of the blood is rich in proteins that perform immnulogical functions, such
as the complement proteins that inform phagocytic cells about a pathogen and also trigger
production of antibodies.
4. Cytokines- these are the proteins produced by the epithelial cells (dendritic cells), neutrophils,
macrophages that control the growth and spread of infection.
CHARACTERISTICS
&
DEFENSES

6. INNATE
IMMUNITY
TYPES OF INNATE IMMUNITY
1. Species Immunity: Species immunity (species resistance) is that in which a disease affecting one
species does not affect the other species. For convenience, humans do not contract cattle plague,
chicken cholera, hog cholera, infectious horse anaemia, etc., while animals are not affected by many
human diseases such as enteric fever, scarlet fever, syphilis, gonorrhoea, measles, etc.
2. Racial Immunity: Racial immunity (racial resistance) is that in which various races (breeds) show
marked differences in their resistance to certain infectious diseases. A well known example is that
Brahman cattle are resistant to the protozoan parasite responsible for tick fever in other breeds of
cattle. Similarly, Black Africans affected by sickle cell anaemia, a genetic disease, are resistant to
malaria while malaria affects other human races.
3. Individual Immunity: Having the same racial background and opportunity for exposure, some
individuals of the race experience fewer or less severe infections than other individuals of the same
race. For convenience, children are more susceptible to diseases such as measles and chicken pox,
while aged individuals are susceptible to other diseases like pneumonia.
TYPES

7. ACQUIRED
IMMUNITY
CHARACTERISTICS
• Based upon resistance acquired during life
• Relies on genetic events and cellular growth
• Responds more slowly, over few days
• Is specific- each cell responds to a single epitope on an antigen
• Has anamnestic memory- repeated exposure leads to faster, stronger response
• Leads to clonal expansion
CHARACTERISTICS
&
CARDINAL
FEATURES
CARDINAL FEATURES
1. Tolerance to self antigens - under normal conditions, an immune response to "self" antigens
(called an autoimmune response) does not occur.
2. Specificity – components of adaptive immunity react specifically with the antigen that induced
their formation.
3. Memory - the adaptive immunological response remembers the antigen for invariable period of
time and upon subsequent exposure to homologous antigen there is an anamnestic immune
response, i.e. strengthens upon repeated exposure

8. ACQUIRED
IMMUNITY
CLASSIFICATION ACQUIRED
IMMUNITY
NATURAL
ARTIFICIAL
ACTIVE
PASSSIVE
NATURAL
ARTIFICIAL
MODE OF
DEVELOPMENT
EFFECTOR
MOLECULES
HUMORAL
CELL MEDIATED

10. ACQUIRED
IMMUNITY
ACQUIRED ACTIVE IMMUNITY
Active immunity is created by our own immune system when we are exposed to a potential disease-
causing agent (i.e., pathogen). Most of the time, we are exposed to these potential pathogens
naturally throughout the course of our day — in the air we breathe, the food we eat, and the things
we touch
TYPES OF ACQUIRED ACTIVE IMMUNITY
1. NATURALLY ACQUIRED ACTIVE IMMUNITY- Naturally acquired active immunity occurs when the
person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the
primary immune response. Once a microbe penetrates the body’s skin, mucous membranes, or other
primary defenses, it interacts with the immune system. B-cells in the body produce antibodies that
help to fight against the invading microbes. The adaptive immune response generated against the
pathogen takes days or weeks to develop but may be long-lasting like tetnus, or even lifelong like
chiken pox
2. ARTIFICIALLY ACQUIRED ACTIVE IMMUNITY- It is protection produced by intentional exposure of a
person to antigens in a vaccine, so as to produce an active and lasting immune response. The antigens
in the vaccine stimulate the immune system to produce antibodies and memory cells which
are specifically directed against the antigens in the vaccine. After the immunization, if the living
infectious agents with the same antigens that were in the vaccine get into the person’s body, the
correct antibodies are already present and they bind to the infectious agents. The memory cells
generate a rapid immune response from the rest of the immune system, and the infectious agents are
quickly attacked and destroyed, often before symptoms of the disease can develop.
ACTIVE
IMMUNITY

11. ACQUIRED
IMMUNITY
ACQUIRED PASSIVE IMMUNITY
Passive immunity refers to the process of providing IgG antibodies to protect against infection; it
gives immediate, but short-lived protection—several weeks to 3 or 4 months at most.
TYPES OF ACQUIRED PASSIVE IMMUNITY
1. NATURALLY ACQUIRED PASSIVE IMMUNITY -Maternal passive immunity is a type of naturally
acquired passive immunity, and refers to antibody-mediated immunity conveyed to a fetus or infant
by its mother. Naturally acquired passive immunity can be provided during pregnancy, and
through breastfeeding. In humans, maternal antibodies (MatAb) are passed through the placenta to
the fetus by an FcRn receptor on placental cells.
2. ARTIFICIALLY ACQUIRED PASSIVE IMMUNITY- Artificial immunity is a mean by which the body is
given immunity to a disease by intentional exposure to small quantities of it. The most common
form of artificial immunity is classified as active and comes in the form of antibiotics or lab made
immunity, typically given to children and young adults.The passive form of artificial immunity
involves introducing an antibody into the system once a person has already been infected with a
disease, ultimately relieving the present symptoms of the sickness and preventing re-
occurrence.Once the body has successfully rid itself of a disease caused by a certain pathogen, a
second infection with the same pathogen would prove harmless.
PASSIVE
IMMUNITY

12. ACQUIRED
IMMUNITY
HUMORAL IMMUNITY
• Humoral or antibody mediated immunity (AMI) is characterized by the production of antigen
specific immunoglobulin molecules, called as ‘antibodies’, induced in response to an antigen and
is mediated by B lymphocytes. Antibodies primarily defend against extracellular pathogens and
toxins. Humoral immunity is so named because it involves substances found in the humors, or
body fluids.
• Humoral immunity is also called antibody-mediated immunity. With assistance from helper T
cells, B cells will differentiate into plasma B cells that can produce antibodies against a specific
antigen. The humoral immune system deals with antigens from pathogens that are freely
circulating, or outside the infected cells . Whenever naïve B cells encounter an antigen in the
lymphatic system, they undergo a differentiation process that leads to the creation of memory B
cells and effector B cells.
HUMORAL
IMMUNITY

13. ACQUIRED
IMMUNITY
CELL MEDIATED IMMUNITY
• Cell-mediated immunity (CMI) involves the activation of antigen-specific cells, such as CTLs and
macrophages, which destroys the cells harboring antigen. Cellular immunity primarily defend
against intracellular pathogens, multicellular parasites, transplanted tissue, and cancer cells.
• Cell-mediated immunity does not depend on antibodies for its adaptive immune functions. Cell-
mediated immunity is primarily driven by mature T cells, macrophages, and the release of
cytokines in response to an antigen.
• cell-mediated immunity, so named because the T cells themselves latch onto the antigens of
the invader and then initiate reactions that lead to the destruction of the nonself matter. B
lymphocytes, on the other hand, do not directly attack invaders. Rather, they produce
antibodies, proteins that are capable of initiating reactions that weaken or destroy the foreign
substance.
CELL MEDIATED
IMMUNITY

14. ACQUIRED
IMMUNITY
HUMORAL vs CELL
MEDIATED
IMMUNITY

15. IMMUNITY THANK YOU