Question:
Read the following statements regarding the complement system. Choose the set of correct statements about appropriate properties of complement
(A). Complement activity is destroyed (inactivated) by heating serum at 56 \(^{\circ}\)C for 30 minutes.
(B). Complement activity opsonize bacteria for enhanced phagocytosis and facilitate lysis of the bacteria
(C). Complement is non antibody heat stable serum proteins
(D). Complement comprises over 20 different serum proteins that are produced by a variety of cells including, hepatocytes, macrophages and gut epithelial cells.
Choose the correct answer from the options given below:
Read the following statements regarding the complement system. Choose the set of correct statements about appropriate properties of complement
(A). Complement activity is destroyed (inactivated) by heating serum at 56 \(^{\circ}\)C for 30 minutes.
(B). Complement activity opsonize bacteria for enhanced phagocytosis and facilitate lysis of the bacteria
(C). Complement is non antibody heat stable serum proteins
(D). Complement comprises over 20 different serum proteins that are produced by a variety of cells including, hepatocytes, macrophages and gut epithelial cells.
Choose the correct answer from the options given below:
(A). Complement activity is destroyed (inactivated) by heating serum at 56 \(^{\circ}\)C for 30 minutes.
(B). Complement activity opsonize bacteria for enhanced phagocytosis and facilitate lysis of the bacteria
(C). Complement is non antibody heat stable serum proteins
(D). Complement comprises over 20 different serum proteins that are produced by a variety of cells including, hepatocytes, macrophages and gut epithelial cells.
Choose the correct answer from the options given below:
Show Hint
Statements (A) and (C) directly contradict each other regarding heat stability.
Since heating serum at \(56\ ^{\circ}\text{C}\) inactivates complement, they must be heat-labile.
Thus, Statement (C) must be false, which immediately eliminates options containing (C) and leaves Option (A) as the only logical answer.
Since heating serum at \(56\ ^{\circ}\text{C}\) inactivates complement, they must be heat-labile.
Thus, Statement (C) must be false, which immediately eliminates options containing (C) and leaves Option (A) as the only logical answer.
Updated On: Aug 3, 2026
- (A), (B) and (D) only.
- (A), (B) and (C) only.
- (A), (C) and (D) only.
- (B), (C) and (D) only.
Show Solution
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
This question addresses the complement system, a crucial biochemical cascade of the innate immune system that helps or "complements" the ability of antibodies and phagocytic cells to clear pathogens from an organism.
To evaluate this question, we must analyze the physical stability, functional roles, and cellular origins of these proteins.
Step 2: Detailed Explanation:
Let us evaluate each statement individually to determine its scientific validity:
- Statement (A): "Complement activity is destroyed (inactivated) by heating serum at 56 \(^{\circ}\)C for 30 minutes."
This statement is correct. Complement proteins are highly heat-labile (heat-sensitive).
In laboratory diagnostics and cell culture, heating serum to \(56\ ^{\circ}\text{C}\) for 30 minutes is the standard protocol used to selectively inactivate complement proteins while preserving the relatively heat-stable immunoglobulins (antibodies).
- Statement (B): "Complement activity opsonize bacteria for enhanced phagocytosis and facilitate lysis of the bacteria"
This statement is correct. The activation of the complement cascade leads to several key immunological outcomes:
1. Opsonization: Complement fragments (specifically C3b and C4b) bind covalently to the bacterial cell wall. Phagocytes (neutrophils and macrophages) express complement receptors (like CR1) that bind these opsonins, dramatically enhancing phagocytosis.
2. Lysis: The late stages of the complement cascade lead to the assembly of the Membrane Attack Complex (MAC, composed of C5b, C6, C7, C8, and multiple C9 proteins). The MAC forms pores in the bacterial cell membrane, causing osmotic lysis.
- Statement (C): "Complement is non antibody heat stable serum proteins"
This statement is incorrect. While complement proteins are indeed non-antibody serum proteins, they are highly heat-labile (as established in Statement A), not heat-stable.
- Statement (D): "Complement comprises over 20 different serum proteins that are produced by a variety of cells including, hepatocytes, macrophages and gut epithelial cells."
This statement is correct. The complement system is composed of more than 20 to 30 distinct circulating soluble proteins and membrane-bound regulators.
The primary site of complement synthesis is the liver (specifically hepatocytes).
However, significant local synthesis of complement components also occurs in extrahepatic cells, including tissue macrophages, blood monocytes, and epithelial cells of the gastrointestinal and genitourinary tracts.
Therefore, statements (A), (B), and (D) are correct, while statement (C) is incorrect.
Step 3: Final Answer:
The correct set of statements is (A), (B), and (D) only.
Therefore, the correct choice is Option (A).
This question addresses the complement system, a crucial biochemical cascade of the innate immune system that helps or "complements" the ability of antibodies and phagocytic cells to clear pathogens from an organism.
To evaluate this question, we must analyze the physical stability, functional roles, and cellular origins of these proteins.
Step 2: Detailed Explanation:
Let us evaluate each statement individually to determine its scientific validity:
- Statement (A): "Complement activity is destroyed (inactivated) by heating serum at 56 \(^{\circ}\)C for 30 minutes."
This statement is correct. Complement proteins are highly heat-labile (heat-sensitive).
In laboratory diagnostics and cell culture, heating serum to \(56\ ^{\circ}\text{C}\) for 30 minutes is the standard protocol used to selectively inactivate complement proteins while preserving the relatively heat-stable immunoglobulins (antibodies).
- Statement (B): "Complement activity opsonize bacteria for enhanced phagocytosis and facilitate lysis of the bacteria"
This statement is correct. The activation of the complement cascade leads to several key immunological outcomes:
1. Opsonization: Complement fragments (specifically C3b and C4b) bind covalently to the bacterial cell wall. Phagocytes (neutrophils and macrophages) express complement receptors (like CR1) that bind these opsonins, dramatically enhancing phagocytosis.
2. Lysis: The late stages of the complement cascade lead to the assembly of the Membrane Attack Complex (MAC, composed of C5b, C6, C7, C8, and multiple C9 proteins). The MAC forms pores in the bacterial cell membrane, causing osmotic lysis.
- Statement (C): "Complement is non antibody heat stable serum proteins"
This statement is incorrect. While complement proteins are indeed non-antibody serum proteins, they are highly heat-labile (as established in Statement A), not heat-stable.
- Statement (D): "Complement comprises over 20 different serum proteins that are produced by a variety of cells including, hepatocytes, macrophages and gut epithelial cells."
This statement is correct. The complement system is composed of more than 20 to 30 distinct circulating soluble proteins and membrane-bound regulators.
The primary site of complement synthesis is the liver (specifically hepatocytes).
However, significant local synthesis of complement components also occurs in extrahepatic cells, including tissue macrophages, blood monocytes, and epithelial cells of the gastrointestinal and genitourinary tracts.
Therefore, statements (A), (B), and (D) are correct, while statement (C) is incorrect.
Step 3: Final Answer:
The correct set of statements is (A), (B), and (D) only.
Therefore, the correct choice is Option (A).
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