SCSA Human Biology Response to infection

Direct contact transmission requires physical contact between an infected person and a susceptible person, not an intermediate organism like a mosquito.

Droplet transmission occurs when respiratory droplets from coughing or sneezing carry pathogens directly to a susceptible person, which does not involve a mosquito.

Airborne transmission involves pathogens traveling through the air over time and distance, rather than being delivered by a biting insect.

Complement proteins circulate in the blood in an inactive state and must be triggered by specific pathways (such as the presence of pathogens or antibodies) to become activated.

The complement system is primarily part of the innate immune system and is activated by antibodies or pathogen surfaces, not by helper T cells.

While some complement byproducts can trigger histamine release to promote inflammation, complement proteins are endogenous immune components, not foreign allergens.

While some viruses mutate and change their surface proteins to evade the immune system, this is not why antibiotics fail. Antibiotics target specific cellular machinery, which viruses lack entirely.

Although some viruses are enveloped in host cell membranes, this is not the reason antibiotics are ineffective. Antibiotics fail because they target bacterial structures, not because the virus is disguised.

Viruses do not consume food or possess metabolic enzymes. While some resistant bacteria can degrade antibiotics, viruses are completely incapable of metabolizing them.

Natural active immunity occurs when a person's own immune system produces antibodies in response to a natural infection, rather than receiving them from another source.

Artificial passive immunity involves receiving pre-made antibodies through medical intervention, such as an injection of immunoglobulins or antivenom.

Artificial active immunity is acquired through vaccination, which medically introduces an antigen to stimulate the body's own immune system to produce antibodies.

The goal of humanising an antibody is not to decrease its binding strength, as strong binding to the target antigen is necessary for its therapeutic effect.

Monoclonal antibodies are designed to specifically target cancer cells, so increasing the destruction of non-cancerous cells would be a harmful side effect, not an advantage.

Delivering toxic substances less effectively would reduce the efficacy of the treatment, which is a disadvantage rather than an advantage.

Horses do not typically eat fruit as a primary food source. The virus is transmitted through bat bodily fluids, which are more likely to contaminate exposed feed and water rather than just fruit.

Capturing and vaccinating an entire wild population of fruit bats is logistically impossible and therefore not a practical solution.

Destroying the food source of fruit bats would cause severe ecological damage and could actually force bats to relocate closer to human and horse populations in search of food.

While eosinophils are involved in allergic reactions and parasitic infections, they primarily release toxic granule proteins and other inflammatory mediators rather than being the main source of histamine.

Macrophages are phagocytic cells responsible for engulfing and digesting pathogens and cellular debris; they do not release histamine.

Natural killer cells are cytotoxic lymphocytes that identify and destroy virus-infected or cancerous cells, not cells that release histamine during an allergic response.

Relenza works by inhibiting neuraminidase to prevent viral release, but since MERS lacks this protein, the drug would not affect the release of MERS viral particles.

Because MERS does not have the neuraminidase protein that Relenza targets, the drug would be completely ineffective as a preventative measure.

Relenza is highly specific to neuraminidase and does not target or bind to other cell surface proteins on infected cells.

Innate immunity is the non-specific defense system present from birth, and active immunity requires the body to produce its own antibodies. Receiving an injection of pre-formed antibodies is neither.

Natural passive immunity involves the natural transfer of antibodies, such as from a mother to her fetus across the placenta or through breast milk, rather than through a medical injection.

Acquired active immunity occurs when the body's immune system is stimulated to produce its own antibodies, typically through vaccination with an antigen, not by receiving pre-formed antibodies.

Antigens are typically foreign substances (like viral or bacterial proteins) that trigger an immune response, rather than a defensive component produced by the body.

Antibodies are the primary component of humoral immunity, not cell-mediated immunity, and are produced by B cells to target extracellular pathogens.

Memory B cells are part of the humoral immune response, which relies on the production of antibodies rather than direct cell-to-cell combat.

This order incorrectly starts with isolating the microorganism before first establishing its presence in diseased animals and absence in healthy ones.

This sequence is incorrect because it suggests isolating the microorganism before confirming it is exclusively found in diseased animals.

This order is incorrect because it places the re-isolation of the microorganism from the experimental animal before actually infecting the healthy experimental animal.