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Let’s first know about an immune system before stressing on what is active and passive immunity.

Let’s first know about an immune system before stressing on what is active and passive immunity. The basic defense system of the body is called an immune system. It protects us from harmful pathogens and diseases. It consists of various types of cells and different proteins that kill the harmful invading microorganisms to protect from the disease. The Function of an Immune System It prevents or limits an infection; when our immunity or immune system recognizes pathogens, it addresses a problem. When an immune system is not activated, problems like infections and diseases arise. When an immune system is activated without a real danger or is not turned off when a threat passes, problems arise such as allergic reactions and autoimmune disease.   What is Active and Passive Immunity? Two different categories of our immune system are:

Active Immunity Definition – It is the immunity where the body produces its own antibodies when a body is exposed to that disease.  It allows an immune system to recognize a disease which will then trigger our body to fight against it. It is often long-lasting and may sometimes give us life-long protection against diseases. Passive Immunity Definition – It is a type of immunity that is provided when a person is given antibodies from outside. It provides immediate protection but doesn’t guarantee long-term protection like active immunity.   Let’s Differentiate Between Active And Passive Immunity Active and passive immunity difference can be understood with the help of a tabular representation as follows:  

  Image will be updated soon   Examples of Active and Passive Immunity Below are a few examples of active and passive immunity that can make us understand both categories in a better manner.  

Understanding the basic structure of an immune system, it consists of three layers of defense to protect from infection Barrier immunity Eg: Skin is a physical barrier as well as chemical and biological barrier as it produces antimicrobial proteins; Surface lining of the respiratory system has cilia for preventing pathogens and building up of microorganisms; Stomach release strong acids with low pH and kills microorganisms that we accidentally ingest while eating; tears also is an example of barrier immunity as it protects our eyes from dust and pathogens. Innate immunity When a microorganism is successful in crossing barrier immunity, innate immunity is activated. Innate immunity is non-specific and is present before birth. Neutrophils, mast cells, basophils, dendritic cells, eosinophils, natural killer cells, monocytes, and macrophages are different innate cells.   Acquired or Adaptive Immunity It is the third line of defense and produced in exposure to foreign substances. It is a specific immune system that consists of highly specialised systemic cells and processes that eliminate pathogens and prevent its growth. It adapts to the type of threat that we are exposed to; it produces lymphocytes and antibodies during second exposure which are specific to pathogens when exposed to the first exposure. It is slower in the process but more potent than innate immunity. Immunological memory of the first encounter is produced while second exposure, thus lymphocytes and antibodies are present to eliminate pathogens. SImilarly for subsequent exposures. B lymphocytes and T lymphocytes are two kinds of lymphocytes.

In Humoral immunity, B lymphocytes produce Antibodies that capture antigens present on the surface of bacteria or pathogens. Antigen-specific antibodies are produced on the second exposure. T-lymphocytes consist of two major cells known as helper T cells that are known as CD4 cytotoxic and killer t cells known as CD8 cells.

Q1. What is an Adjuvant? It is a substance that is known to be hyper-irritating to the immune system when it is added in an attempt to facilitate a more robust response with more memory cells. Example- Mercury. Q2. What is the major active and passive immunity difference? Active immunity takes place when the host produces antibodies when exposed to pathogens or bacteria while passive immunity takes place when the host receives antibodies from another source. Q3. Give a few examples of active and passive immunity. Immunization of chickenpox, hepatitis, flu, and polio are some examples of active immunity. A baby receiving antibodies from her mother’s breast milk and injection of antisera are examples of passive immunity. Q4. What is the active immunity definition? Active immunity is a state where antibodies are developed in a person’s own immune system after the body is exposed to an antigen through disease or when he or she gets an immunization, for example- A flu shot. Q5. What is the passive immunity definition? Passive immunity is a state where antibodies are given to a person to prevent or fight against disease or to treat disease after the body is exposed to an antigen. For example, during pregnancy, the placental transfer of IgG from a mother to fetus takes place that generally lasts 4 to 6 months after birth; and also human breast milk that comprises the IgA and IgG in the colostrum.

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The host receives antibodies from another source.

The host’s own body will make antibodies when exposed to pathogens; lymphocytes form memory cells.

It doesn’t generate immunological memory.

It may consist of certain side-effects when it is given externally.

It has no side-effects and doesn’t cause chemical reactions.


Baby receiving antibodies (IgG) from the mother during the third trimester of pregnancy.

Breast Milk that contains IgA antibodies in addition to other Abs.

Immunoglobulin injection, for example, is given after rabies exposure.


When a body is exposed to the pathogens in everyday life, passive immunity is triggered.

Exposure of the body to some part of the pathogen in a vaccine such as:

Live attenuated vaccine (MMR)

Deactivated toxins from a pathogen (Corynebacterium diphtheria toxin, Clostridium tetani toxin)

Part of the bacterial cell (Bordetella pertussis and streptococcus pneumonia)