Acquired Immunity: Humoral, Cell-Mediated, Active and Passive
Acquired immunity is pathogen-specific immunity developed after exposure to an antigen, involving lymphocytes, antibodies, memory cells, and primary or secondary immune responses.
In one line: Active means your body acts; passive means protection is passed to you.
Concept Practice Coming SoonUnderstand it
- Acquired immunity is specific and has memory.
- B-lymphocytes produce antibodies, giving humoral immunity through body fluids.
- T-lymphocytes support cell-mediated immunity, which is important against infected cells and in graft rejection.
- The primary response after first antigen exposure is slower and weaker, while the secondary response is faster and stronger because memory cells are already present.
- Active immunity develops when the body produces its own antibodies after infection or vaccination.
- Passive immunity is received ready-made, such as maternal antibodies or injected antibodies, and gives quick but usually short-term protection.
Example
Rule to remember
Immune response rule: first exposure forms primary response and memory cells; later exposure triggers faster secondary response.
Active immunity makes antibodies; passive immunity receives antibodies.
See it worked out
Follow the example line by line, then use the same method on new questions.
Worked example
Question: A person receives antivenom after a snake bite.
- 1Identify the immunity.
- 2Answer: It is passive immunity because ready-made antibodies are supplied for immediate protection.
Method you can reuse
- 1Define acquired immunity.
- 2Mention antigen specificity and memory.
- 3Explain B-cell antibody response as humoral immunity.
- 4Explain T-cell response as cell-mediated immunity.
- 5Compare primary and secondary responses.
- 6Distinguish active and passive immunity using source, speed, duration, and memory.
Visual tip
A graph of antibody concentration versus time is important. Labels should include first exposure, primary response, memory cells, second exposure, secondary response, antibody level, and time.
Check yourself
Answer the question in your head before opening the answer.
Try it yourself
Why is the secondary immune response faster than the primary response?
Think first, then show answerHide answer
Common wrong answer
Calling vaccination passive immunity.
Why it loses marks: Vaccination stimulates the body to produce its own immune response and memory cells.
Don't mix this up
Exam tip
Write it in the exam
Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.
How CBSE asks it
Answer plan
- 1
Enough for 1 mark
Acquired immunity is pathogen-specific immunity developed after exposure to an antigen, involving lymphocytes, antibodies, memory cells, and primary or secondary immune responses.
- 2
Add for 2 marks
Example: A child receiving a vaccine develops active immunity because the child's immune system forms antibodies and memory cells. A newborn receiving maternal antibodies through colostrum receives passive immunity.
- 3
Add for 3 marks
Acquired immunity is specific and has memory.
Concept practice is coming soon
Login to access concept-level MCQs and weak-concept practice as they become available.
Help improve this page
Found something confusing, incorrect, or missing?