What Is Natural Immunity: All You Need to Know

What is natural immunity¹? This question is often asked, so let’s read the article to know.

Immunity in biology refers to an organism’s capacity to fend off harmful microbes. Both specific and generic components contribute to natural immunity. Regardless of their antigenic makeup, the nonspecific components serve as barriers to or eliminators of natural infection and artificial infections. Other immune system responses can develop pathogen-specific immunity by adjusting to each new illness.

Immunity can discriminate between native and foreign and tolerate both (non-self).

1) Innate and Adaptive

The immune system is innate and adaptive. Only vertebrates have adaptive immunity.

When the immune system responds to non-self molecules, inflammatory reactions and phagocytosis occur. Adaptive lymphocytes may recognize “non-self” substances when “self” is present. Inflammation is the response to foreign compounds, while immunity is the non-reaction to self-substances.

Native immunity is another name for innate immunity, which develops natural immunity. It’s the body’s first line of protection against infection, helping to maintain homeostasis and stimulate an adaptive immune response. Instead of adjusting to environmental stimuli or previous infection, it detects genetically imprinted patterns.

Antigen-specific lymphocytes mediate adaptive immunity². Acquired immunity comprises immunological memory and is pathogen-specific. Like the innate system, the acquired system has humoral and cell-mediated immunity.

Natural infection or artificial ways (through deliberate actions such as vaccination) can create adaptive immunity. Active and passive are a part of adaptive immunity. By being exposed to a pathogen, one can build active natural immunity. Passive immunity is achieved by the transfer of protective antibodies or activated T-cells from an immune host. It is temporary and requires booster doses for sustained natural immunity.

2) History of Active Immune Response

In 1798, Edward Jenner invented the safer way of deliberately infecting people with the cowpox virus (smallpox vaccine) to induce natural immunity to smallpox (vaccine-induced immunity). By 1800, vaccines were used. Smallpox inoculation became known as variolation, regardless of date, to minimize misunderstanding.

Jenner’s approach drove the development of vaccination by Pasteur and others in the late 19th century. Pasteur broadened the concept of vaccination in 1891 to honor Jenner, and it became necessary to specify the polio vaccine, measles vaccine, etc.

The first clinical report of immunity from a specific disease-causing organism is presumably Al-Treatise Razi’s on Smallpox and Measles (9th century). Al Razi discusses the clinical presentation of smallpox and measles and shows exposure to them gives lifelong higher protection (although he does not use this term).

3) Passive Immunity

Passive immunity³ is acquired by transferring already-made antibodies. This immunity can develop spontaneously when maternal antibodies are transferred to the fetus through the placenta. It can be chemically generated by giving non-immune persons extremely concentrated human (or horse) antibodies specific to a disease or toxin.

Passive immunization is applied when there is a greater risk of infection and not enough time for the body to mount an immune response. It can reduce chronic or immunosuppressive symptoms. It offers temporary protection, but the patient is still susceptible to future infections from the same virus.

3.1) Types of Passive Immune Responses

1) Natural Immunity – What is Natural Immunity?

Fetus passively gets natural immunity from the mother during pregnancy. Passive immunity is antibody-mediated. An FcRn receptor on placental cells transfers MatAb from the mother to fetus. This happens around the third month. Only IgG can pass the placenta.

IgA antibodies from breast milk protect a nursing infant’s gut from bacterial infections until the baby can produce antibodies. Mother’s milk includes colostrum which is an example of passive immunity.

2) Artificial Acquired Passive Immunity

Artificially acquired passive immunity (AAPI) is a temporary immunization by transmitting antibodies. These can be given in a variety of ways, including as pooled human immunoglobulin for intravenous (IVIG) or intramuscular (IG) use, as human or animal blood plasma, and as monoclonal antibodies (MAb).

Hypogammaglobulinemia is prevented via passive transmission. Poisoning and acute infections are also treated by it. Passive immunization produces transitory immunity and can cause hypersensitivity reactions and serum sickness, especially with non-human gamma globulin.

Before the development of antibiotics, artificial induction of passive immunity was frequently the only treatment for some illnesses. It has been used for more than a century to treat infectious diseases. Despite the development of sulfonamide lot antibiotics, immunoglobulin therapy remained the first-line therapy for some severe diseases until the 1930s.

4) Active Immunity

Pathogens excite B and T cells, which triggers the immunological response. Memory cells “remember” each infection an animal meets and can develop a strong secondary reaction. Glenny described primary and secondary responses in 1921, but the mechanism was subsequently established. Adaptive natural immunity prepares us for future threats. Cell-mediated, humoral, and innate immunities are active.

4.1) Active Immunity Types

1) Natural Immunity

When exposed to a live virus, a person generates a basic immune reaction and immunological memory. Immunodeficiency (acquired and congenital) and immunosuppression can impact natural immunity in force.

2) Artificially Acquired

Antigen-containing vaccine immunity can generate force natural immunity. A vaccination induces an antigen response without inducing disease symptoms. Louis Pasteur adopted the phrase vaccination from Edward Jenner’s colleague Richard Dunning. Pasteur treated infectious agents so they couldn’t cause sickness. Pasteur adopted the name vaccination as a generic term to honor Jenner’s discovery.

Bavaria was the first to impose smallpox vaccinations for military recruits in 1807. Vaccination increased as war spread.

4.2) Some Traditional Vaccinations

a) Inactivated vaccinations include destroyed microorganisms that are no longer contagious. Flu, cholera, plague, and hepatitis A vaccinations are examples. Most of these immunizations need boosters.

b) Live, attenuated vaccines include microorganisms that can’t cause disease. Yellow fever, measles, rubella, and mumps are examples. Durable responses may need booster shots.

c) Toxoids are inactivated microorganism toxins administered before exposure to the microorganism’s toxin. Tetanus and diphtheria are toxoid-based vaccinations.

d) Subunit, recombinant, polysaccharide, and conjugate vaccines include pathogen fragments. Subunit Hepatitis B vaccination is an example.

5) Hybrid Immunity

Natural immunity and artificial immunity combine to create hybrid immunity. Hybrid-immune people’s blood neutralizes Beta and SARS-CoV-2’s other variants better than fully vaccinated but never vaccinated persons.

On October 29, 2021, the Centers for Disease Control and Prevention (CDC) decided that infection with SARS-CoV-2 and vaccination each result in a low risk of subsequent infection with antigenically identical variations for at least 6 months.

According to research, numerous immunologic and epidemiologic studies (CDC study) suggest that vaccination of previously infected persons dramatically boosts their immune response and reduces the likelihood of recurrent infection, even in more infectious variations.

6) Herd Immunity

It is a sort of indirect protection against contagious diseases. It occurs when a sufficient fraction of a population is immune to infection from prior infection or vaccination, lowering the chance of infection for others without natural immunity. It is also known as ‘Community Immunity.’

7) Covid-19

COVID-19⁴, often known as the coronavirus pandemic, was a global epidemic caused by a coronavirus (SARS-CoV-2). The novel virus was discovered in Wuhan, China, in December 2019. The virus spread to other parts of China and the world despite attempts to contain it. It was a severe disease that took thousands of lives.

The Covid 19 epidemic caused tremendous social and economic devastation worldwide, including the biggest global recession since the Great Depression. Due to this Covid 19, people’s lives were at greater risk. But later on, Covid 19 vaccines proved beneficial. The source of Covid 19 was bats.

Alpha variant and Delta variant are new, dangerous covid 19. The WHO declared the outbreak a pandemic on March 11, 2020. As of September 20, 2022, the pandemic caused more than 612 million illnesses and 6.52 million deaths.

Many countries tried to delay or stop COVID-19 by advocating, requiring, or restricting behavior changes, while others provided information. Elimination and mitigation were outbreak-control tactics under Covid 19. Public advisories and lockdowns were implemented.

Elimination strategies (commonly known as “zero-COVID”) aim to stop the spread of the virus within the community completely, while mitigation strategies (widely known as “flattening the curve”) attempt to lessen the effects of the virus on society but still tolerate some level of transmission within the community.

7.1) Covid-19 Vaccines Work

Since December 2020, COVID-19 vaccinations have been widely distributed (Mass Vaccination) to develop immunity. MAb, antivirals, Johnson vaccine, and symptom control are included in the treatments. Social distance, masks, improved ventilation, air filtration, and quarantining of exposed or symptomatic people are also recommended.

Travel restrictions, lockdowns, company limitations and closures, occupational hazard controls, quarantines, testing systems, and tracing sick connections were government interventions due to Covid 19.

Covid 19 vaccine confers SARS-CoV2 protection (coronavirus disease 2019), (Covid 19). Before Covid 19, scientists understood SARS and MERS’ structure and function. This led to the 2020 Covid 19 vaccine platform. SARS-CoV-2 vaccinations targeted severe symptoms.

On January 10, 2020, the Global Initiative on Sharing Avian Influenza Data (GISAID) revealed the SARS-CoV-2 genetic sequence data, and by March 19, the global pharmaceutical sector committed to addressing COVID-19. The Covid 19 vaccine immunity reduced disease severity and fatality of the delta variant and other variants of Covid 19.

By late December 2021, nearly 4.49 billion people in 197 nations had one or two doses of covid 19 vaccine to protect themselves from illness. Most people utilized the Oxford-AstraZeneca vaccination. Unvaccinated people were not permitted to travel; only fully vaccinated people were allowed to go out.

7.2) Treatment of Covid-19

No specific therapy or cure was provided for the first two years of the Covid 19 pandemic. In 2021, the European Medicines Agency’s (EMA) committee, CHMP, authorized Paxlovid (nirmatrelvir with ritonavir) to treat adult patients. FDA granted EUA later.

Covid 19 was moderate. These include paracetamol or NSAIDs to ease symptoms (fever, body pains, and cough). Oral fluids, rest, personal cleanliness, and good eating were also advised.

Supportive care comprises symptom relief, hydration therapy, oxygen support, prone positioning, and drugs or devices to support other organs. In hospitals for severe Covid 19 cases, Dexamethasone reduces mortality in patients with low oxygen levels.

Noninvasive and mechanical ventilation in an ICU may be needed to maintain breathing. Covid vaccines prove to be very useful this time. ECMO (Extracorporeal membrane oxygenation) addresses respiratory failure.

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2. Mehling, Matthias, et al. “Antigen‐specific adaptive immune responses in fingolimod‐treated multiple sclerosis patients.” Annals of neurology 69.2 (2011): 408-413. ↩︎
3. Keller, Margaret A., and E. Richard Stiehm. “Passive immunity in prevention and treatment of infectious diseases.” Clinical microbiology reviews 13.4 (2000): 602-614. ↩︎
4. Ciotti, Marco, et al. “The COVID-19 pandemic.” Critical reviews in clinical laboratory sciences 57.6 (2020): 365-388. ↩︎

Last Updated on May 9, 2024 by Namrata