Immunity is the body's ability to resist or fight off infections and diseases.

What are the types of immunity?

There are two main types: innate immunity (the body's first line of defense, including physical barriers like skin) and adaptive immunity (specific responses developed after exposure to pathogens).

Can stress affect my immune system?

Yes, chronic stress can weaken the immune response, making you more susceptible to illness.

Frequently Asked Questions

Join ALLEN!

(Session 2026 - 27)

Name

Mobile Number

Class

Choose class

Goal

Choose your goal

Preferred Programs

Preferred Mode

State

Choose State

I agree to

I authorise ALLEN Career Institute Pvt Ltd to send me regular updates via Phone calls, Whatsapp, SMS, Robocalls (Automated Calls), Emails, or on postal address.

Immunity

The human body has the ability to defend itself against a wide range of organisms and toxins that can harm tissues and organs, a capability known as immunity. This immunity consists of two main components: the less specific innate immunity and the more specific adaptive immunity.

1.0Types of Immunity

Innate Immunity - Innate immunity serves as the body's first line of defense against infections. Most components of innate immunity are present prior to any infection and consist of a range of disease-resistance mechanisms that are not tailored to specific pathogens. Instead, they include cellular and molecular elements that identify common molecules found in frequently encountered pathogens. Innate immunity encompasses four main types of defensive barriers:

Anatomic
Physiologic
Phagocytic
Inflammatory

Also Read: Diversity in Living Organisms

Summary of nonspecific host defenses
Type	Mechanism
Skin	Mechanical barriers prevent the entry of microbes. An acidic environment (pH 3-5) inhibits microbial growth.
Mucous membranes	Protective role by trapping foreign microorganisms, while normal flora compete with pathogens for attachment sites and nutrients. Additionally, cilia help propel microorganisms out of the body, forming an essential part of physiological barriers.
Physiological barriers
Temperature	Normal body temperature helps inhibit the growth of certain pathogens, while fever responses further enhance this effect.
Low pH	The low pH of stomach contents effectively kills most ingested microorganisms.
Chemical mediators	Lysozyme breaks down bacterial cell walls. Interferon triggers an antiviral state in uninfected cells. Complement proteins can lyse microorganisms or enhance phagocytosis. Toll-like receptors detect microbial molecules, prompting cells to secrete immunostimulatory cytokines. Collections disrupt the cell walls of pathogens.
Phagocytic/endocytic barriers	Specialized cells, including blood monocytes, neutrophils, and tissue macrophages, internalize (endocytose) and degrade foreign macromolecules through phagocytosis, allowing them to engulf, kill, and digest entire microorganisms.
Inflammatory barriers	Tissue damage and infections trigger the leakage of vascular fluid containing serum proteins with antibacterial properties, along with the influx of phagocytic cells to the affected area.

Adaptive Immunity - Adaptive immunity does not come into play until there is an antigenic challenge to the organism. It is capable of recognizing and selectively eliminating specific foreign microorganisms and molecules (i.e., foreign antigens). Unlike innate immune responses, adaptive immune responses are not the same in all species but are reactions to specific antigenic challenges.

Adaptive immunity displays four characteristic attributes:

Antigenic specificity
Diversity
Immunologic memory
Self/nonself recognition
The Adaptive Immune System Requires Cooperation between Lymphocytes and Antigen-Presenting Cells.
Lymphocytes are one of many types of white blood cells produced in the bone marrow by the process of hematopoiesis .
Lymphocytes leave the bone marrow, circulate in the blood and lymphatic systems, and reside in various lymphoid organs.
Because they produce and display antigen binding cell-surface receptors, lymphocytes mediate the defining immunologic attributes of specificity, diversity, memory, and self/nonself recognition.
The two major populations of lymphocytes—B lymphocytes (B cells) and T lymphocytes (T cells).

Acquired immunity consists of two key components:

T lymphocytes, which mediate cellular immunity
humoral immunity, which is mediated by circulating immunoglobulin antibodies found in the plasma's γ-globulin fraction. These immunoglobulins, produced by differentiated B lymphocytes known as plasma cells, activate the complement system and help neutralize and eliminate antigens.

Image showing the classification of immunity

2.0Signs of Weak Immune System

Feeling Tiredness
Frequent fever and chills
Frequent Diarrhea
Feeling Stress
Poor Wound healing
Frequent Infections
Sudden High Fevers
Muscle and Joint Aches
Frequently on Medication for one Illness or the other
Severe hair loss
Skin infections

Also Read:

Genetics and Evolution	Neuron and nerves	CD4 Cells
Malaria	Respiratory system	AIDS
Prevention of Sexually Transmitted Diseases (STDs)	Body Fluids and Circulation	Composition of Blood

Join ALLEN!

(Session 2026 - 27)

Name

Mobile Number

Class

Choose class

Goal

Choose your goal

Preferred Programs

Preferred Mode

State

Choose State

I agree to

I authorise ALLEN Career Institute Pvt Ltd to send me regular updates via Phone calls, Whatsapp, SMS, Robocalls (Automated Calls), Emails, or on postal address.

Immunity

The human body has the ability to defend itself against a wide range of organisms and toxins that can harm tissues and organs, a capability known as immunity. This immunity consists of two main components: the less specific innate immunity and the more specific adaptive immunity.

1.0Types of Immunity

Innate Immunity - Innate immunity serves as the body's first line of defense against infections. Most components of innate immunity are present prior to any infection and consist of a range of disease-resistance mechanisms that are not tailored to specific pathogens. Instead, they include cellular and molecular elements that identify common molecules found in frequently encountered pathogens. Innate immunity encompasses four main types of defensive barriers:

Anatomic
Physiologic
Phagocytic
Inflammatory

Also Read: Diversity in Living Organisms

Summary of nonspecific host defenses
Type	Mechanism
Skin	Mechanical barriers prevent the entry of microbes. An acidic environment (pH 3-5) inhibits microbial growth.
Mucous membranes	Protective role by trapping foreign microorganisms, while normal flora compete with pathogens for attachment sites and nutrients. Additionally, cilia help propel microorganisms out of the body, forming an essential part of physiological barriers.
Physiological barriers
Temperature	Normal body temperature helps inhibit the growth of certain pathogens, while fever responses further enhance this effect.
Low pH	The low pH of stomach contents effectively kills most ingested microorganisms.
Chemical mediators	Lysozyme breaks down bacterial cell walls. Interferon triggers an antiviral state in uninfected cells. Complement proteins can lyse microorganisms or enhance phagocytosis. Toll-like receptors detect microbial molecules, prompting cells to secrete immunostimulatory cytokines. Collections disrupt the cell walls of pathogens.
Phagocytic/endocytic barriers	Specialized cells, including blood monocytes, neutrophils, and tissue macrophages, internalize (endocytose) and degrade foreign macromolecules through phagocytosis, allowing them to engulf, kill, and digest entire microorganisms.
Inflammatory barriers	Tissue damage and infections trigger the leakage of vascular fluid containing serum proteins with antibacterial properties, along with the influx of phagocytic cells to the affected area.

Adaptive Immunity - Adaptive immunity does not come into play until there is an antigenic challenge to the organism. It is capable of recognizing and selectively eliminating specific foreign microorganisms and molecules (i.e., foreign antigens). Unlike innate immune responses, adaptive immune responses are not the same in all species but are reactions to specific antigenic challenges.

Adaptive immunity displays four characteristic attributes:

Antigenic specificity
Diversity
Immunologic memory
Self/nonself recognition
The Adaptive Immune System Requires Cooperation between Lymphocytes and Antigen-Presenting Cells.
Lymphocytes are one of many types of white blood cells produced in the bone marrow by the process of hematopoiesis .
Lymphocytes leave the bone marrow, circulate in the blood and lymphatic systems, and reside in various lymphoid organs.
Because they produce and display antigen binding cell-surface receptors, lymphocytes mediate the defining immunologic attributes of specificity, diversity, memory, and self/nonself recognition.
The two major populations of lymphocytes—B lymphocytes (B cells) and T lymphocytes (T cells).

Acquired immunity consists of two key components:

T lymphocytes, which mediate cellular immunity
humoral immunity, which is mediated by circulating immunoglobulin antibodies found in the plasma's γ-globulin fraction. These immunoglobulins, produced by differentiated B lymphocytes known as plasma cells, activate the complement system and help neutralize and eliminate antigens.

2.0Signs of Weak Immune System

Feeling Tiredness
Frequent fever and chills
Frequent Diarrhea
Feeling Stress
Poor Wound healing
Frequent Infections
Sudden High Fevers
Muscle and Joint Aches
Frequently on Medication for one Illness or the other
Severe hair loss
Skin infections

Also Read:

Genetics and Evolution	Neuron and nerves	CD4 Cells
Malaria	Respiratory system	AIDS
Prevention of Sexually Transmitted Diseases (STDs)	Body Fluids and Circulation	Composition of Blood

Frequently Asked Questions

What is immunity?

What are the types of immunity?

Can stress affect my immune system?

Frequently Asked Questions

What is immunity?

What are the types of immunity?

Can stress affect my immune system?

Join ALLEN!

Immunity

1.0Types of Immunity

2.0Signs of Weak Immune System

Table of Contents

Join ALLEN!

Immunity

1.0Types of Immunity

2.0Signs of Weak Immune System

Table of Contents