Question:
Which complement component acts as an opsonin?
Which complement component acts as an opsonin?
Show Hint
The larger cleavage fragment of C3 coats bacteria for phagocytosis.
Updated On: Jun 24, 2026
- C3a
- C3b
- C5a
- C6
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Step 1: Opsonisation is the coating of a foreign particle so that phagocytes can recognise and engulf it. The coating molecules are called opsonins.
Step 2: C3 is the most abundant complement protein and is cleaved into C3a and C3b. The fragment that attaches to bacterial surfaces and tags them for phagocytosis is C3b. So C3b is the opsonin and the correct answer.
Step 3: Other complement opsonins include iC3b and C4b, and antibodies (IgG) also act as opsonins.
Step 4: The distractors have different roles: C3a and C5a are anaphylatoxins that trigger mast cell and basophil histamine release and chemotaxis, and C6 is part of the membrane attack complex, not an opsonin.
Step 2: C3 is the most abundant complement protein and is cleaved into C3a and C3b. The fragment that attaches to bacterial surfaces and tags them for phagocytosis is C3b. So C3b is the opsonin and the correct answer.
Step 3: Other complement opsonins include iC3b and C4b, and antibodies (IgG) also act as opsonins.
Step 4: The distractors have different roles: C3a and C5a are anaphylatoxins that trigger mast cell and basophil histamine release and chemotaxis, and C6 is part of the membrane attack complex, not an opsonin.
Was this answer helpful?
0
0
Top NEET PG Pathology Questions
- Which of the following is true regarding the Mendelian mode of inheritance?
- A child presents with intermittent jaundice and splenomegaly. There is a history of similar complaints in the elder brother. Peripheral smear shows the following finding. How will you investigate this condition?
- An African child is found to have a mass in the jaw. A biopsy of the mass was done, and it appears as shown in the image below. The child also had a translocation of t(8;14). What is the probable diagnosis?
- A child presented to the hospital with cola-colored urine, hypertension, and puffiness of eyes. Laboratory investigations were done, and creatinine was 2.5 mg/dL. Treatment was started, and despite treatment, the patient did not improve for the next 3 weeks. The creatinine value increased to 4.5 mg/dL. Which among the following electron microscopic findings will be seen in this patient ?
- A patient was transfused 4 units of blood 2 hours ago, and now she complains of chest discomfort. X-ray shows bilateral fissural thickening. Which of the following is the most probable cause ?
View More Questions
Top NEET PG Questions
- A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
- Which of the following statements is true about Trichomonas vaginalis?
- A lady from West Rajasthan presented with an ulcer surrounded by erythema on the right leg. Microscopy of the biopsy from the edge of the ulcer showed organisms with dark staining nuclei and kinetoplast. What is the most likely causative agent?
- A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?
- Infection with Clonorchis sinensis is associated with an increased risk of__?
View More Questions