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Human Health and Diseases - Innate and Acquired Immunity

Grade 12CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Innate Immunity: A non-specific type of defense present at the time of birth. It consists of four barriers: Physical (e.g., Skin, Mucus), Physiological (e.g., HClHCl in stomach, saliva), Cellular (e.g., PMNLPMNL-neutrophils, Monocytes), and Cytokine (Interferons).

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Acquired Immunity: Pathogen-specific immunity characterized by memory. The first encounter with a pathogen results in a low-intensity 'Primary Response', while subsequent encounters result in a highly intensified 'Secondary' or 'Anamnestic Response'.

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Humoral Immune Response: Mediated by B-lymphocytes that produce antibodies in the blood plasma. The basic structural representation of an antibody molecule is H2L2H_{2}L_{2}.

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Cell-Mediated Immunity (CMI): Mediated by T-lymphocytes. This system is responsible for the rejection of organ grafts as it can distinguish between 'self' and 'non-self' tissues.

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Active Immunity: Occurs when a host is exposed to antigens (living or dead microbes) and the body produces its own antibodies. It is slow but provides long-lasting protection.

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Passive Immunity: Occurs when readymade antibodies are directly given to protect the body. Examples include IgAIgA found in colostrum and the transfer of antibodies through the placenta (IgGIgG).

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Interferons (IFNIFN): Proteins secreted by virus-infected cells which protect non-infected cells from further viral infection.

📐Formulae

H2L2H_{2}L_{2}

Primary Response≪Secondary (Anamnestic) Response\text{Primary Response} \ll \text{Secondary (Anamnestic) Response}

Antigen+Antibody→Ag-Ab Complex\text{Antigen} + \text{Antibody} \rightarrow \text{Ag-Ab Complex}

💡Examples

Problem 1:

A newborn baby receives certain antibodies from the mother's milk (colostrum). Identify the type of immunity and the specific antibody involved.

Solution:

Passive Immunity; IgAIgA.

Explanation:

Colostrum is rich in antibodies of the IgAIgA type. Since the baby is receiving readymade antibodies rather than producing them, it is classified as natural passive immunity.

Problem 2:

Explain why a person who has recovered from Measles is unlikely to suffer from it again in their lifetime.

Solution:

Due to 'Acquired Immunity' and 'Immunological Memory'.

Explanation:

During the first infection (Primary response), the body produces B and T memory cells. When the same pathogen attacks again, these cells trigger a highly intensified secondary/anamnestic response that neutralizes the pathogen before symptoms appear.

Problem 3:

An organ transplant patient must take immunosuppressants for the rest of their life. Which type of immunity is responsible for this necessity?

Solution:

Cell-Mediated Immunity (CMI).

Explanation:

T-lymphocytes are responsible for CMI, which allows the body to recognize foreign tissue. Without immunosuppressants, the CMI would recognize the transplanted organ as 'non-self' and initiate graft rejection.