MDS PREP
The opsonins which leads to phagocytosis is/are:
1. lgG (Fc fragment)
2. C3b of complement cascade
3. 1gM (Fc fragment) and C5b of complement cascade
4. A and B
Pathology
Answer: 4
Opsonins are molecules that enhance the phagocytosis of antigens by binding to their surfaces and acting as markers or labels that make them more recognizable to phagocytes.
1. lgG (Fc fragment): Immunoglobulin G (IgG) is the most common antibody isotype
in human serum. It plays a crucial role in the secondary immune response. The Fc
region of IgG is the fragment that interacts with Fc receptors present on the
membrane of phagocytic cells. When an antigen is coated with IgG, the Fc
fragments of these antibodies can bind to the Fc receptors, leading to the
activation of the phagocytic process. This is known as antibody-dependent
phagocytosis, where the antibody acts as an opsonin to facilitate the
recognition and engulfment of the antigen by phagocytic cells.
2. C3b of complement cascade: The complement system is a cascade of proteins
that can be activated in response to an infection or the presence of foreign
substances. C3 is a central protein in this system, and when it is cleaved into
C3a and C3b, the latter can bind directly to antigens. C3b acts as an opsonin by
coating the surface of pathogens. The presence of C3b on a microbial surface
allows it to be recognized by complement receptors on phagocytic cells, such as
macrophages. This interaction enhances the efficiency of phagocytosis, as the
receptors can recognize the bound C3b and engulf the antigen more readily.
3. IgM (Fc fragment) and C5b of complement cascade: While IgM is the first
antibody isotype produced in response to an infection and can also opsonize
antigens, it is less efficient than IgG due to its pentameric structure and
lower affinity for phagocytic receptors. However, it is not as commonly
associated with phagocytosis as IgG. Regarding C5b, it is part of the membrane
attack complex (MAC) and is involved in the direct destruction of pathogens
rather than acting as a classical opsonin that leads to phagocytosis. The MAC
assembles on the surface of the antigen and creates pores, leading to osmotic
lysis and destruction of the cell membrane.
All of the following can cause osteoporosis, except
1. Hyperparathyroidism
2. Steroid use
3. Fluorosis
4. Thyrotoxicosis
Oral Pathology
Answer: 3
Fluorosis does not cause osteoporosis.
Osmotic fragility is increased in -
1) Sickle cell anaemia
2) Thalassemia
3) Hereditary spherocytosis
4) Chronic lead poisoning
General Pathology
Answer: 3
Osmotic fragility is increased in hereditary spherocytosis due to the abnormal shape and membrane stability of red blood cells.
What condition is typically characterized by a malar rash, arthritis, serositis, and the presence of antinuclear antibodies?
1) Goodpasture's syndrome
2) Friedreich ataxia
3) Huntington's disease
4) Systemic lupus erythematosus (SLE)
Systemic lupus erythematosus (SLE) is characterized by a malar rash, arthritis, serositis, and the presence of antinuclear antibodies.
The extracellular polysaccharide synthesized by cariogenic streptococci in the presence of excess sucros is best described as
1) Mucopolysaccharide
2) Dextran-like glucan
3) Glycogen-like glucan
4) Amylopectin
Oral Pathology
Answer: 2
Cariogenic streptococci, particularly Streptococcus mutans, synthesize extracellular polysaccharides when exposed to high levels of sucrose. These polysaccharides are primarily dextran-like glucans, which are formed from the polymerization of glucose units. Dextran contributes to the formation of dental plaque and biofilm, facilitating the adherence of bacteria to tooth surfaces and promoting caries development.
The maximum permissible dose of radiation to the operator of an X-ray machine is
1. 0.05 rem per year
2. 0.5 rem per year
3. 5.0 rem per year
4. 50 rem per year
Oral Pathology
Answer: 3
The maximum permissible dose of radiation to the operator of an X-ray machine is 5.0 rem per year.
Disadvantages of using a GRID during radiography is
1. Increased patient exposure
2. Decreased exposure time
3. Increased secondary radiation fog to film
4. Reduces secondary radiation to film
Oral Pathology
Answer: 1
Using a GRID during radiography increases patient exposure due to the need for higher doses.
Precocious puberty is most characteristic of which of the following/
1. Jaffe"s syndrome
2. Monostotic fibrous dysplasia
3. Polyostotic fibrous dysplasia
4. Albright"s syndrome
Oral Pathology
Answer: 4
Precocious puberty is most characteristic of Albright's syndrome.