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Human Health and Disease — BIOLOGY STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 ScienceBIOLOGYHuman Health and Disease4 Marks
Question
Explain: Acquired Immunity.
✓

Answer

→Acquired immunity, on the other hand, is pathogen specific. It is characterised by memory.
→This means that our body, when encounters a pathogen for the first time, produces a response called primary response which is of low intensity.
→Subsequent encounter with the same pathogen elicits a highly intensified secondary or anamnestic response.
→The primary and secondary immune responses are carried out with the help of two special types of lymphocytes present in our blood, i.e., B-lymphocytes and T- lymphocytes.
Image
→There are two type of acquired immune response.
→(i) Antibody Mediated Immune response or / Humoral Immune response."
→The B-lymphocytes produce an army of proteins in response to pathogens into our blood to fight with them. These proteins are called antibodies.
→The T-cells themselves do not secrete antibodies but help B cells produce them.
→Each antibody molecule has four peptide chains, two small called light chains and two longer, called heavy chains."
→Hence, an antibody is represented as H2L2. Different 22 types of antibodies are produced in our body
→IgA, IgM, IgE, IgG are some of them. A structure of an antibody is given in Figure 7.4. Because these antibodies are found in the blood, the response is also called humoral immune response.
(ii) Cell Mediated Immune response
→The second type is called cell-mediated immune response or cell- mediated immunity (CMI). The T-lymphocytes mediate CМІ.

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