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Human Physiology (UPCAT-Dental)

Description: Lymphatic system and Immune system
Number of Questions: 25
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Tags: Lymphatic system and Immune system Human Physiology
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In human beings, a primary lymphoid organ is a place where immune cells of the body develops and matures to the stage at which they are able to respond to a pathogen. Which one of the following is/are primary lymphoid organ(s) of the human body?

  1. Lymph nodes

  2. Spleen

  3. Peyer's patch

  4. Tonsils

  5. Thymus


Correct Option: E
Explanation:

T-cells are derived from bone marrow stem cells and differentiate into immunocompetent cells in the thymus.

A lymphocyte is a type of white blood cell that is part of the immune system. Which among the following specialised cell types is involved in the entry of lymphocytes into lymph nodes of the body?

  1. M-cells

  2. Mesangial cells

  3. PALS

  4. HEV endothelial cells

  5. Selectins


Correct Option: D
Explanation:

The high-walled endothelium of the post-capillary venules (HEV) in lymph nodes express vascular addressins, which are recognised by homing receptors on lymphocytes passing through the afferent lymphatics and which mediate entry of the lymphocytes into the lymph nodes.

Pattern recognition receptors are a primitive part of the immune system of the human beings. These receptors generally include

  1. LPS

  2. PAMPs

  3. Lipoteichoic acid

  4. Lectin-like molecules

  5. Unmethylated CpG sequences


Correct Option: D
Explanation:

Many PRR are lectin-like in that they recognise exposed microbial sugars.

Mononuclear phagocyte system is based on analogies in the morphology, function, origin, and dynamics of the phagocytes. Which among the following can be excluded from the mononuclear phagocyte system?

  1. Monocytes

  2. Kupffer cells

  3. Kidney mesangial cells

  4. Lymph node medullary macrophages

  5. Endothelial cells


Correct Option: E
Explanation:

Endothelial cells are not essentially phagocytic, although they do contribute by the production of mediators of the inflammatory process, particularly acute inflammation and were previously lumped together with the mononuclear phagocyte system in what is known as the reticuloendothelial system (RES).

Neutrophil Defensins induces histamine secretion from the mast cells. They are generally

  1. peptide antibiotics

  2. oxygen-dependent

  3. glycolipids

  4. enzymes

  5. anti-toxins


Correct Option: A
Explanation:

The defensins are peptide antibiotics present in the granules in extremely high concentration.

The paracortical area of a lymph node engrosses mainly which of the following cells?

  1. Follicular dendritic cell

  2. Plasma cells

  3. Macrophages

  4. B-cells

  5. T-cells


Correct Option: E
Explanation:

T-cells are mainly confined to the paracortical (thymus-dependent) area of lymph nodes, and in nodes taken from children with selective T-cell deficiency. The paracortical region is virtually devoid of lymphocytes.

Which of the following statements regarding a polymorphonuclear neutrophil (PMN) is true?

  1. It is a bone marrow stem cell.

  2. It contains microbicidal cytoplasmic granules.

  3. It is closely similar to a mast cell.

  4. It is not a professional phagocytic cell.

  5. It has granules, which stain with eosin.


Correct Option: B
Explanation:

The granules contain a wide spectrum of microbicidal agents.

The membrane-attack complex (MAC) of complement pathway and perforin (PF) are important tools deployed by the immune system to target pathogens. The membrane-attack complex consists of

  1. OH

  2. Colicins

  3. C5b,6,7,8,9

  4. C3b3b,Bb

  5. Properdin


Correct Option: C
Explanation:

These terminal components form a complex, which inserts into the membrane to form a transmembrane ion channel, which leads to lysis of the cell.

Acute inflammation inside the body characteristically causes

  1. constriction of arterioles

  2. capillary endothelial cell enlargement

  3. influx of macrophages

  4. influx of neutrophils

  5. influx of mast cells


Correct Option: D
Explanation:

Neutrophils are chemotactically attracted to the site of inflammation by C5a and mast cell chemotactic factors such as leukotriene B4.

Complement component C3 plays a central role in the activation of complement system. Which among the following can cleave complement component C3?

  1. C3b

  2. C3bBb

  3. Factor B

  4. Factor D

  5. Factor H


Correct Option: B
Explanation:

This is the C3 convertase enzyme generated in the alternative complement pathway and is responsible for splitting off the small peptide C3a, leaving C3b as a residue.

Which of the following is not an acute phase protein?

  1. Serum amyloid P component

  2. Chondroitin sulfate

  3. C-reactive protein

  4. Mannose binding lectin

  5. Fibrinogen


Correct Option: B
Explanation:

This is a cell matrix component.

NK cells play a major role in the host-rejection of both tumours and virally infected cells. Which among the following does not characterise Natural Killer (NK) cells of the human body?

  1. Respond to interferon

  2. Contain perforin

  3. Kill only by damaging the target cell outer membrane

  4. Contain tumour necrosis factor (TNF)

  5. Contain serine proteases


Correct Option: C
Explanation:

Perforin inserts into the target cell membrane, thereby facilitating entry of TNF and granzymes into the target cell.

Apoptosis is defined as the process of programmed cell death. An example of an anti-apoptotic molecule is

  1. Bcl-2

  2. TRAIL

  3. Bax

  4. FADD

  5. Caspase 8


Correct Option: A
Explanation:

Molecules such as Bcl-2 and Bcl-XL prevent the release of pro-apoptotic proteins from mitochondria. Note, however, that some members of the Bcl-2 family, such as bid, have pro-apoptotic functions.

Which of the following statements is true regarding the cardiovascular system in a developing fetus?

  1. Blood pressure = stroke volume X heart rate

  2. Left-to-right shunting across the duct is normal in the fetus.

  3. The fetal heart does not start pumping blood until the completion of first trimester.

  4. In a developing fetus, the contractility of the heart is independent of preload and afterload.

  5. The ductus arteriosus can be kept open by the use of certain medicines including indomethacing.


Correct Option: D
Explanation:

Unlike stroke volume, contractility is independent of preload and afterload and is an innate property of myofibrils. It can be influenced by inotropes (e.g. dobutamine).

Hydrops fetalis is an excess accumulation of fluid in the fetus. Which one of the following conditions is least likely to present as hydrops fetalis?

  1. Alpha thalassemia

  2. Beta thalassemia

  3. ABO incompatibility

  4. Rhesus isoimmunisation

  5. Twin-to-twin transfusion


Correct Option: B
Explanation:

Classic β-thalassaemia major does not affect neonates because most of the haemoglobin is in the fetal (HbF) form.

Which one of the following factors does not decrease the perinatal mortality rate?

  1. Improved antenatal care

  2. Lower social class

  3. Improved maternal health

  4. Prenatal care and counselling

  5. Maternal education


Correct Option: B
Explanation:

Lower social class significantly increases the risk of perinatal mortality.

In new borns, lack of vitamin K causes hemorrhagic disease. Which one of the following is the most common cause of late-onset haemorrhagic disease?

  1. Neonatal septicaemia

  2. Complete oral (instead of IM) vitamin K administration

  3. Formula feeding

  4. Cystic fibrosis

  5. Hypoxic–ischaemic encephalopathy


Correct Option: D
Explanation:

Infants with undiagnosed cystic fibrosis can have malabsorption of the fat soluble vitamins (Vit A, E, D and K) and this would be the most likely cause of late-onset haemorrhagic disease in this list.

Which of the following lymphoid tissues is unencapsulated?

  1. Thymus

  2. Lymph node

  3. Spleen

  4. Tonsil

  5. MALT


Correct Option: E
Explanation:

The respiratory, alimentary and genitourinary tracts are guarded immunologically by subepithelial accumulations of lymphoid tissues, which are not constrained by a connective tissue capsule. These may occur as diffuse collections of lymphocytes, plasma cells and phagocytes throughout the body and the lamina propria of the intestinal wall or as more clearly organised tissue with well-formed follicles as found in the Peyer's patches.

Which one of the following does not increase the rate of perinatal loss?

  1. Female sex of fetus

  2. Low birth weight

  3. Multiple pregnancy

  4. Maternal age < 20 years

  5. Maternal age > 40 years


Correct Option: A
Explanation:

Females have a slightly lower rate of perinatal mortality. All the other factors are known to increase the perinatal mortality rate.

Which of the following diseases in the newborn is not a indication of maternal IgG antibody, crossing the placenta?

  1. Myaesthenia gravis

  2. Malar rash

  3. HIV infection

  4. Thyrotoxicosis

  5. Haemolytic disease of the newborn (rhesus)


Correct Option: C
Explanation:

HIV infection is due to transmission of the HIV virus, not the antibody. However, the presence of maternal anti-HIV IgG can lead to diagnostic difficulty. It is therefore, necessary to confirm HIV infection in the newborn by the presence of viral DNA or RNA, using a polymerase chain reaction (PCR) method.

A heavy chain is the large polypeptide sub-unit of a protein complex. The first immunoglobulin heavy chain class to be manifested on the surface of a newly produced B-cell in the body is

  1. IgA

  2. IgD

  3. IgE

  4. IgG

  5. IgM


Correct Option: E
Explanation:

IgM is the first immunoglobulin class to be expressed on the surface of the developing B-cells, shortly followed by IgD. Early mature B-cells co-express IgM and IgD antibodies of identical antigen specificity.

The variable region of a heavy chain immunoglobulin is encoded by three DNA segments, VH (variable), D (diversity) and JH (joining). What is the approximate number of D segment genes in the immunoglobulin heavy chain gene locus?

  1. 40

  2. 30

  3. 9

  4. 6

  5. 1


Correct Option: B
Explanation:

D regions are only found in the heavy chain; the light chain gene loci lack D segments.

Langerhans cells are found in the epidermis layer of the skin. These are generally found in

  1. lymph

  2. lymph nodes

  3. periarteriolar lymphoid sheaths

  4. skin

  5. mantle zone


Correct Option: D
Explanation:

Langerhans' cells in the skin pick up and process antigen, then travel as veiled cells in the lymph before becoming interdigitating dendritic cells in the paracortical T-cell zone of the draining lymph node, where they are potent stimulators of T-cell responses.

Which of the following can be excluded from the functions of macrophages?

  1. Pinocytosis

  2. Phagocytosis

  3. Antigen processing

  4. T-cell priming

  5. Antigen presentation to activated cells


Correct Option: D
Explanation:

Macrophages have an impressive range of functions, but appear unable to prime naive lymphocytes. This can be carried out by lymphoid interdigitating dendritic cells and cultured, but not freshly isolated, Langerhans' cells.

Which among the following is a major factor in controlling the adaptive immune response of the body?

  1. Neutrophil

  2. Complement membrane attack complex

  3. C-reactive protein

  4. Antigen concentration

  5. Haptoglobin


Correct Option: D
Explanation:

Lymphocytes are directly driven by antigen. The concentration of antigen is important because the binding to the surface of responding B-cells is necessary for continued stimulation. As the antigen concentration falls through catabolism or neutralisation or complex formation with antibody, the immune response diminishes. In this way, the immune response is not maintained at a high level when the antigen has been eliminated.

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