Sources of Passive Immunity

Passive immunity refers to the transfer of pre-formed antibodies from one individual to another to provide temporary protection against a specific pathogen. Unlike active immunity, which is acquired through the production of antibodies by the individual’s own immune system, passive immunity offers immediate but temporary protection without the need for an individual’s immune response.

Passive immunity can occur naturally or be acquired artificially. Natural passive immunity is observed when a fetus receives antibodies from its mother via the placenta. These antibodies provide protection against various infections during the early stages of life when the baby’s immune system is still developing. Additionally, breastfeeding also provides passive immunity as the mother’s antibodies are passed on to the baby through breast milk.

Artificial passive immunity, on the other hand, is obtained through the administration of pre-formed antibodies derived from another individual or animal. This can be in the form of immunoglobulin injections or specific antibody preparations known as antiserum. These antibodies are collected from individuals who have previously been exposed to the pathogen or have been immunized against it.

Passive immunity is particularly useful in situations where immediate protection is needed or when an individual cannot produce their own antibodies due to a weakened immune system. For example, if someone is exposed to a dangerous infectious disease and does not have sufficient time for their immune system to mount a response, passive immunity can provide temporary protection against the pathogen.

Passive immunity is also used as a preventive measure against certain diseases. For instance, individuals traveling to regions where certain diseases are prevalent may receive passive immunization to protect them during their stay. Additionally, individuals who have been exposed to a particular pathogen, such as a snakebite, may receive antiserum containing specific antibodies to neutralize the venom.

It is important to note that passive immunity is short-lived compared to active immunity. The transferred antibodies eventually degrade and are cleared from the recipient’s body. Therefore, passive immunity provides only temporary protection and does not confer long-term immunity. In contrast, active immunity, obtained through vaccination or previous exposure to the pathogen, stimulates the individual’s immune system to produce its own antibodies, resulting in long-lasting protection.

In conclusion, passive immunity involves the transfer of pre-formed antibodies to provide temporary protection against specific pathogens. It can occur naturally through the transfer of antibodies from mother to fetus or through breastfeeding. It can also be acquired artificially through the administration of immunoglobulin or antiserum. Passive immunity offers immediate protection but is temporary, lasting only as long as the transferred antibodies remain in the body. Active immunity, on the other hand, provides long-term protection as it stimulates the individual’s immune system to produce its own antibodies.


Passive immunity refers to the acquisition of temporary protection against infectious diseases through the transfer of preformed antibodies. Unlike active immunity, which is developed by one’s own immune system in response to an infection or vaccination, passive immunity provides immediate but short-term protection. In this article, we will explore the sources of passive immunity.

1. Maternal Antibodies

1.1 During Pregnancy

One of the primary sources of passive immunity is from a mother to her unborn child during pregnancy. Maternal antibodies, especially immunoglobulin G (IgG), are transferred across the placenta to provide the fetus with protection against certain infections. This passive immunity helps protect the newborn during the early months of life when their own immune system is still developing.

1.2 Through Breast Milk

Breast milk is another important source of passive immunity for infants. It contains various antibodies, including secretory immunoglobulin A (IgA), which are passed from the mother to the baby during breastfeeding. These antibodies help protect the baby’s gastrointestinal and respiratory tracts from infections, providing passive immunity until their own immune system matures.

2. Immunoglobulin Therapy

2.1 Intravenous Immunoglobulin (IVIG)

Intravenous immunoglobulin (IVIG) therapy is a medical treatment that involves the administration of concentrated antibodies derived from the plasma of multiple donors. IVIG is used to provide passive immunity in individuals with primary immunodeficiency disorders or those who have weakened immune systems. It can also be used as a treatment for certain autoimmune and inflammatory conditions.

2.2 Hyperimmune Globulins

Hyperimmune globulins are specialized preparations of antibodies that are highly concentrated against a specific pathogen or toxin. They are derived from the plasma of individuals who have been exposed to or vaccinated against a particular infectious agent. Hyperimmune globulins are used to provide immediate protection against specific diseases, such as hepatitis B, rabies, or tetanus.

3. Convalescent Plasma

3.1 Recovered Patients

Convalescent plasma therapy involves the transfusion of plasma obtained from individuals who have recently recovered from a specific infection. The plasma contains antibodies that the recovered individual developed in response to the infection. By transfusing this plasma into a patient with the same infection, passive immunity can be provided, as the antibodies in the plasma can help fight the pathogen.

Mechanisms of Passive Immunity

Definition and Process

Passive immunity involves the transfer of pre-formed antibodies from one individual to another. These antibodies can neutralize pathogens and provide immediate protection, although this protection is typically short-lived, lasting only a few weeks to months. The key distinction between passive and active immunity is that passive immunity does not involve the recipient’s immune system actively producing the antibodies.

Types of Antibodies

The antibodies involved in passive immunity are typically immunoglobulins (Ig), with the most common being IgG. These antibodies can directly neutralize pathogens, mark them for destruction by other immune cells, or recruit other components of the immune system to combat infections.

Sources of Passive Immunity

Natural Sources

  1. Maternal Antibodies: One of the most common examples of passive immunity occurs naturally when a mother transfers antibodies to her baby. During pregnancy, IgG antibodies cross the placenta and provide the newborn with protection against infections. After birth, breastfeeding continues to supply the infant with antibodies, particularly IgA, which protect against gastrointestinal infections.

Artificial Sources

  1. Immunoglobulin Therapy: Medical treatments can provide passive immunity through the administration of immunoglobulin preparations derived from the plasma of immune individuals. These preparations can be specific (targeting a particular pathogen) or nonspecific (providing broad protection).
  2. Monoclonal Antibodies: These are laboratory-produced molecules engineered to act like natural antibodies. Monoclonal antibodies are used in the treatment and prevention of various diseases, including certain cancers, autoimmune diseases, and infectious diseases.

Advantages of Passive Immunity

Immediate Protection

One of the primary benefits of passive immunity is that it offers immediate protection. This is particularly important in situations where an individual is exposed to a pathogen and does not have the time to develop active immunity.

Use in Immunocompromised Individuals

Passive immunity is especially beneficial for individuals with weakened immune systems who may not respond well to vaccines or cannot wait for their own immune system to respond to an infection.

Prevention of Disease Spread

In outbreak situations, passive immunity can help control the spread of disease by providing immediate protection to those at high risk, such as healthcare workers or individuals in close contact with infected patients.

Applications of Passive Immunity

Disease Prevention

Passive immunity is often used to prevent diseases in individuals who have been exposed to a pathogen but have not yet developed symptoms. For example, immunoglobulin therapy can be administered to individuals exposed to hepatitis B, rabies, or tetanus to prevent the onset of these infections.

Treatment of Active Infections

In some cases, passive immunity can be used to treat ongoing infections. For instance, antivenom is a form of passive immunity used to treat snake bites, and monoclonal antibodies have been used to treat viral infections like COVID-19.

Protection of Newborns and Infants

Maternal antibodies provide newborns and infants with crucial protection during the early months of life when their immune systems are not fully developed. Breastfeeding extends this protection, helping to shield infants from various infections.

Immunodeficiency Disorders

Individuals with certain immunodeficiency disorders may receive regular immunoglobulin therapy to provide ongoing protection against infections. This is a critical treatment for conditions such as primary immunodeficiency diseases, where the body cannot produce adequate antibodies.

Limitations of Passive Immunity

Short Duration of Protection

The protection provided by passive immunity is temporary, as the transferred antibodies are eventually degraded and not replaced. This contrasts with active immunity, which can provide long-lasting protection due to the development of memory cells.

Lack of Memory Response

Passive immunity does not stimulate the immune system to produce memory cells, meaning that once the transferred antibodies are gone, the individual is no longer protected against future exposures to the same pathogen.

Potential for Allergic Reactions

There is a risk of allergic reactions with the administration of immunoglobulin preparations, particularly if they are derived from animal sources. Careful screening and purification processes are used to minimize these risks.


Passive immunity can be acquired through various sources, including maternal antibodies transferred during pregnancy and through breast milk. Immunoglobulin therapies, such as IVIG and hyperimmune globulins, provide temporary protection against specific infections. Convalescent plasma therapy utilizes the antibodies present in the plasma of recovered patients to provide passive immunity. Understanding the sources of passive immunity is crucial for protecting individuals, especially those with weakened immune systems, against infectious diseases.

Passive Immunity

What is passive immunity?

Passive immunity refers to the temporary acquisition of antibodies that provide immediate but short-term protection against a specific pathogen or toxin. This immunity is gained through the transfer of antibodies, rather than the body’s own production of them.

How is passive immunity acquired?

Passive immunity can be acquired in a few ways:

  • Transplacental transfer of maternal antibodies to the fetus during pregnancy
  • Breastfeeding, where antibodies in the mother’s milk are passed to the infant
  • Injection of antibody-containing preparations, such as immunoglobulin or antitoxin

What are the main advantages of passive immunity?

The key benefits of passive immunity include:

  • Rapid onset of protection, within hours or days
  • Effective against specific pathogens or toxins
  • Useful for individuals who cannot produce their own antibodies
  • Provides immediate short-term immunity, before active immunity develops

How long does passive immunity last?

Passive immunity is temporary and typically lasts for a few weeks to a few months, depending on the source. Maternally-derived antibodies may persist for 6-12 months in infants, while injected antibodies generally provide protection for 2-3 weeks.

What are some examples of passive immunity?

Common examples of passive immunity include:

  • Antibodies passed from mother to child during pregnancy or breastfeeding
  • Injections of anti-venom to treat snake bites
  • Infusions of immunoglobulin to treat immunodeficiency disorders
  • Administration of monoclonal antibodies to treat or prevent certain infections

How does passive immunity differ from active immunity?

The key difference is that passive immunity involves the transfer of pre-made antibodies, while active immunity results from the body’s own immune system producing antibodies in response to an infection or vaccination.