1.
Which of the following complement component is the common link in the classical and alternate pathway of the complement system?
Correct Answer
C. C3
Explanation
C3 is the correct answer because it is the common link in both the classical and alternative pathways of the complement system. In the classical pathway, C3 is activated by C1, while in the alternative pathway, C3 is activated by spontaneous hydrolysis. Once activated, C3 plays a central role in the complement cascade by initiating the formation of the membrane attack complex and promoting inflammation and opsonization. Therefore, C3 is the key component that connects both pathways of the complement system.
2.
Which of the following cell types are the most potent activators of native T cells?
Correct Answer
C. Mature dendritic cells
Explanation
Mature dendritic cells are the most potent activators of native T cells. Dendritic cells are important antigen-presenting cells that play a crucial role in initiating and regulating immune responses. They can capture, process, and present antigens to T cells, thereby activating them. Mature dendritic cells are particularly effective in this process as they express high levels of co-stimulatory molecules and cytokines, which are necessary for T cell activation. B cells, follicular dendritic cells, and macrophages also play important roles in immune responses, but mature dendritic cells are known to be the most potent activators of T cells.
3.
All the following statements about carbohydrates antigens are true except:
Correct Answer
A. Good memory response
Explanation
The correct answer is "good memory response." This is because carbohydrates antigens typically do not elicit a strong memory response from the immune system. Unlike proteins or peptides, carbohydrates do not possess the necessary structural complexity to stimulate the production of memory B cells, which are responsible for long-term immune memory. Therefore, while the other statements are true (carbohydrates antigens generally have poor immunogenicity, do not induce T cell independent immunity, and can elicit a polyclonal response), the statement about a good memory response is not applicable to carbohydrates antigens.
4.
Ovalbumin was injected into a rabbit. Which of the following classes of antibiotics are likely to be produced initially?
Correct Answer
C. IgE
Explanation
When ovalbumin is injected into a rabbit, it triggers an immune response. IgE antibodies are typically involved in hypersensitivity reactions and allergic responses. Therefore, it is likely that IgE antibodies would be produced initially in response to the ovalbumin injection.
5.
Peptide-binding site on class I MHC molecules for presenting processed antigens to CD8 T Cells is formed by:
Correct Answer
B. Distal domain of alpha subunit
Explanation
The peptide-binding site on class I MHC molecules for presenting processed antigens to CD8 T cells is formed by the distal domain of the alpha subunit. This domain is responsible for binding to the processed antigen peptide and presenting it to CD8 T cells for immune recognition. The proximal domain of the alpha subunit and the distal domains of the alpha and beta subunits do not play a direct role in forming the peptide-binding site.
6.
Which of the following statement regarding disinfectants is not true:
Correct Answer
D. Phenol is bactericidal and readily inactivated by organic matter
Explanation
Phenol is not readily inactivated by organic matter. Phenol is a potent disinfectant that is effective against a wide range of microorganisms. It is known for its ability to kill bacteria, viruses, and fungi. Unlike some other disinfectants, phenol is not easily inactivated by organic matter, meaning it remains effective even in the presence of organic substances. This property makes phenol a valuable disinfectant in various settings, including healthcare facilities and laboratories.
7.
Culture media used for diagnosis of EHEC O157: H7 is
Correct Answer
B. Sorbitol mac conkey media
Explanation
The correct answer is sorbitol mac conkey media. This culture media is used for the diagnosis of EHEC O157: H7 because it contains sorbitol as a carbohydrate source. EHEC O157: H7 is unable to ferment sorbitol, so when it is grown on this media, it appears colorless or pale instead of the typical pink/red colonies seen with other E. coli strains. This allows for the differentiation and identification of EHEC O157: H7 from other E. coli strains.
8.
Primary receptors for human immunodeficiency virus (HIV) is:
Correct Answer
A. CD4
Explanation
CD4 is the correct answer because it is the primary receptor for the human immunodeficiency virus (HIV). HIV infects and destroys CD4 T cells, which are a type of white blood cell that plays a crucial role in the immune system. The virus attaches to the CD4 receptor on the surface of these cells, enters them, and replicates, leading to the progressive weakening of the immune system and the development of acquired immunodeficiency syndrome (AIDS). CD8, CD56, and CD3 are not the primary receptors for HIV.
9.
All of the following are functions of CD4 helper cells except:
Correct Answer
B. Produce immunoglobulins
Explanation
CD4 helper cells are a type of immune cell that play a crucial role in coordinating the immune response. They help activate other immune cells, such as macrophages and cytotoxic cells, to fight off infections. Additionally, CD4 helper cells are involved in the development of immunogenic memory, which allows the immune system to remember and respond more effectively to future infections. However, CD4 helper cells themselves do not directly produce immunoglobulins, which are antibodies produced by B cells. Therefore, the correct answer is "produce immunoglobulins."
10.
Which of the following is most resistant to antiseptics:
Correct Answer
B. Prion
Explanation
Prions are the most resistant to antiseptics among the given options. Prions are infectious proteins that can cause diseases in animals and humans. They are highly resistant to disinfection methods, including antiseptics and sterilization techniques. This resistance is due to their unique structure and ability to withstand harsh conditions. Prions can survive in the environment for long periods, making them difficult to eliminate and control.
11.
Which of the following statements about gram-positive cocci is false:
Correct Answer
C. Most enterococci are sensitive to pencillin
Explanation
Enterococci are known to have intrinsic resistance to penicillin. They possess a penicillin-binding protein that has low affinity for penicillin, making them less susceptible to its effects. Therefore, the statement that most enterococci are sensitive to penicillin is false.
12.
Which of the following statements about prion is true:
Correct Answer
A. They are infectious proteins
Explanation
Prions are infectious proteins that can cause a variety of neurodegenerative diseases, such as Creutzfeldt-Jakob disease and mad cow disease. Unlike bacteria and viruses, prions do not have DNA or RNA, and they are not made up of cells. Prions are misfolded versions of normal cellular proteins, and they can convert normal proteins into the misfolded form, leading to the accumulation of abnormal proteins in the brain. Prions cannot be cultured in cell-free media, as they require living cells for replication.
13.
A young male patient presented with UTI on urine examination pus cells were found but no organisms. Which method would be best used for culture?
Correct Answer
A. Mc Coy culture
Explanation
The Mc Coy culture would be the best method to use for culture in this case because it is specifically designed for the isolation and cultivation of fastidious organisms, which are difficult to grow using other culture methods. Since the urine examination showed the presence of pus cells but no organisms, it suggests the possibility of a fastidious organism causing the UTI. Therefore, using the Mc Coy culture would provide the optimal conditions for the growth and identification of these organisms.
14.
Which one of the following is true:
Correct Answer
D. Nutrient broth is a basal medium
Explanation
The statement "nutrient broth is a basal medium" is true. A basal medium is a type of culture medium that provides all the essential nutrients necessary for the growth of microorganisms. Nutrient broth is a commonly used basal medium that contains a rich blend of nutrients such as peptone, beef extract, and water. It supports the growth of a wide range of microorganisms and is often used for general cultivation, maintenance, and propagation of bacteria and other microorganisms in laboratory settings.
15.
Component of innate immunity that is active against viral cells includes:
Correct Answer
A. NK cells
Explanation
NK cells, also known as natural killer cells, are a component of the innate immune system that plays a crucial role in defending against viral infections. These cells are able to recognize and destroy virus-infected cells directly, without the need for prior activation or specific antigen recognition. NK cells release cytotoxic granules that induce apoptosis in the target cells, effectively eliminating the viral infection. This innate immune response is important in the early stages of viral infections before the adaptive immune system, including cytotoxic T cells and B cells, can mount a specific response.
16.
Irradiation can be used to sterIlize A/E.
Correct Answer
D. Bronchoscope
Explanation
Irradiation can be used to sterilize bone grafts, sutures, and artificial tissue grafts. However, bronchoscopes cannot be sterilized using irradiation. Bronchoscopes are delicate instruments used for examining the airways and lungs, and they cannot withstand the high levels of radiation required for sterilization. Therefore, alternative methods such as chemical disinfection or steam sterilization are used to ensure the cleanliness and safety of bronchoscopes.
17.
Antigen-antibody precipitation is maximally seen in which of the following?
Correct Answer
C. Equivalance of antibody and antigen
Explanation
Antigen-antibody precipitation occurs when there is an optimal ratio of antibody and antigen present. This means that the amount of antibody and antigen is equal, resulting in the formation of immune complexes that are large enough to precipitate out of solution. When there is an excess of antibody, the immune complexes may not form and precipitate. Similarly, when there is an excess of antigen, the immune complexes may not form due to limited availability of antibodies. Antigen hapten interaction refers to the binding of a small molecule (hapten) to an antibody, which does not result in precipitation. Therefore, the correct answer is equivalence of antibody and antigen.
18.
All are except regarding Widal test ,except:
Correct Answer
C. O antibody lasts longer and hence is not indicative of recent infection
Explanation
The correct answer is "O antibody lasts longer and hence is not indicative of recent infection." This statement is true because O antibody, also known as the agglutinin antibody, is a long-lasting antibody that can persist in the body for a long time even after the infection has resolved. Therefore, the presence of O antibody does not necessarily indicate a recent or active infection. On the other hand, the other statements are false. Baseline titres can differ depending on the endemicity of the disease, a high titre value in a single Widal test can be confirmative of infection, and H antibody can differentiate between different types of infections.
19.
Culture media of leptospirosis:
Correct Answer
A. Korthof
Explanation
Korthof is a type of culture media that is commonly used for the isolation and growth of Leptospira, the bacteria that causes leptospirosis. It provides the necessary nutrients and conditions for the bacteria to grow and multiply. Other culture media mentioned, such as Perkin, Tinsdale, and Bakers, are not typically used for culturing leptospirosis bacteria.
20.
All of the following statements are true about bacteriophage except:
Correct Answer
D. It transfer only chromosomal gene
Explanation
Bacteriophages are viruses that infect bacteria and help in the process of transduction. They can transfer both chromosomal genes and genes located on plasmids. However, they do not impart toxigenicity to bacteria.