Biology

Human Immunity and Blood

2,051 Questions

Human immunity and blood questions cover the physiological mechanisms protecting the body against diseases and the components of blood. Topics include blood groups, cell mediated immunity, monoclonal antibodies, and blood coagulation. These biology topics frequently appear in general science sections of competitive exams.

Blood groupsCell mediated immunityMonoclonal antibodiesBlood coagulationCancer immunology

Human Immunity and Blood Questions

Multiple choice

Which among the following options characterises interferons?

  1. They opsonise viruses.

  2. They neutralise viruses.

  3. They play a major role in recovery from viral infections.

  4. They prevent viral entry into cells.

  5. They protect against reinfection with virus.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Interferon inhibits the intracellular replication of viruses.

Multiple choice

Which among the following statements regarding the cytotoxic T-cells of the activated defense mechanism is correct?

  1. They are usually CD4.

  2. They recognise native viral antigen.

  3. They are more readily produced by killed rather than live virus.

  4. They kill viruses directly.

  5. They restrict viral replication.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The killing early on, in the infection of a virally-infected cell prevents the virus from utilising that cell for replication.

Multiple choice

The membrane attack complex is composed of a complex of four complement proteins (C5b, C6, C7 and C8) that bind to the outer surface of the plasma membrane. Individuals lacking C8 or C9 are more prone to get infected from

  1. Haemophilus influenzae

  2. Bacillus anthrax

  3. Vibrio cholerae

  4. Neisseria

  5. Listeria monocytogenes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The membrane attack complex containing C8 and C9 is important for destroying the Neisseria bacterium.

Multiple choice

Which of the following changes in the cell causes inflammation, which is a defensive reaction initiated by infection or tissue injury?

  1. Upregulation of adhesion molecules on endothelial cells and leukocytes

  2. Chemotaxis

  3. IL-8 release

  4. Phagocytosis

  5. Bacterial killing
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Up-regulation of P-selectin leads to binding to sialyl Lewisx on the neutrophil and causes rolling along the endothelium. Upregulation of PAF leads to firm binding to the receptor on the neutrophil and the cell is then subject to chemotactic attraction to pass through the endothelial cells.

Multiple choice

Which among the following mechanisms is not used by trypanosomes to evade the host immune response?

  1. Pre-empting complement defences

  2. Releasing decoy proteins

  3. Varying their surface antigens

  4. Escaping from the phagosome

  5. Completely resisting phagocytosis
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Trypanosomes are susceptible to phagocytosis, although some of the evasion mechanisms they employ will limit the ability of the phagocyte to initially bind the parasite and to subsequently kill the engulfed organism.

Multiple choice

The mucosal surfaces represent the largest area of exposure of the body to external pathogens like bacteria, viruses, protozoans, etc. Which among the following types of immunoglobulins initially protects the mucosal surfaces of the body?

  1. IgG

  2. IgM

  3. IgE

  4. Secretory IgA

  5. IgD
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

IgA with secretory piece is dimeric and is the main Ig which prevents adherence of bacteria to the mucosal surface and opsonizes bacteria for adherence to macrophages with Fc alpha receptors.

Multiple choice

Mycobacterium tuberculosis cells growing in macrophages are filamentous and deficient in FtsZ rings, and are killed by which of the following constituents of defense mechanism?

  1. Complement

  2. Reactive oxygen and nitrogen intermediates

  3. Antibodies

  4. Cytotoxic T-cells

  5. Cytokines released from Th1 cells
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

These mechanisms come into play when the macrophage is activated. Other mechanisms, e.g. peptide defensins and cationic proteins may also contribute to killing.

Multiple choice

The extracellular bacteria are found outside the living cells and can be detected quite easily by the immune system because T-cells can come in contact with them. Extracellular bacteria are killed by which of the following phenomena occurring between the host and the bacteria?

  1. Secreting exotoxins

  2. Impeding inflammatory reactions

  3. Phagocytosis and complement

  4. Toxin neutralisation

  5. C-reactive protein
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Major killing of extracellular bacteria is through phagocytosis and intracellular killing. Complement aids opsonisation of bacteria to facilitate phagocytosis but may also be responsible for the bactericidal action of fresh serum containing antibody on Gram-negative bacteria.

Multiple choice

Which blood group is known as the universal donor?

  1. A

  2. B

  3. AB

  4. O

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Blood group O is known as the universal donor because individuals with type O blood can donate red blood cells to recipients of any blood type (A, B, AB, or O). This is because type O red blood cells lack both A and B antigens on their surface, preventing immune reactions. Type AB is the universal recipient, not donor. Types A and B can only donate to specific matching types.

Multiple choice

Macrophages are the body's first line of defense and have many roles.The protein present on the surface of macrophages is

  1. calnexin

  2. galectins

  3. calreticulin

  4. sialoadhesin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sialoadhesin is a cell adhesion molecule found on the surface of certain cells of the immune system called macrophages. It is found in especially high amounts on macrophages of the spleen, liver, lymph node, bone marrow, colon, and lungs. Also, in patients suffering from rheumatoid arthritis, the protein has been found in great amounts on macrophages of the affected tissues.

Multiple choice

One of the most common and potentially serious bacteria to cause severe ear infections is the pneumococcus. In a lymph node, the antigen pneumococcus polysaccharide SIII leads to _______________________.

  1. lymphocyte proliferation in the paracortex

  2. PALS development

  3. development of cellular hypersensitivity

  4. proliferation in cortical lymphoid follicles

  5. the absence of germinal centers
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Stimulation of antibody-formation by this thymus-independent antigen leads to proliferation in this location with development of germinal centers while the paracortical region remains inactive, reflecting the inability to develop cellular hypersensitivity to the polysaccharide.

Multiple choice

Germinal centers are sites within secondary lymphoid organs where mature B lymphocytes are formed. During the bacterial infection of an eye the tingible bodies inside germinal center macrophages are

  1. DNA fragments

  2. Phagocytosed foreign antigen

  3. A sign of macrophage apoptosis

  4. Bacterial cell wall components are resistant to degradation

  5. VLA molecules
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There is very extensive apoptotic cell death amongst the light zone centrocytes and the resultant DNA fragments are visible as 'tingible bodies' within the macrophages which have phagocytosed the apoptotic lymphocytes.