Some people suffer from severe allergic rhinitis (hay fever), which causes frequent sneezing and nasal congestion. Pharmacologists have developed a novel nasal spray containing an IgE-inhibitor that targets specific immunoglobulin receptors on immune cells to prevent allergic responses.
Complete these sentences to describe how the immune system recognises and responds to foreign pathogens.
Use words from the list. Each word can be used once, more than once, or not at all.
Pathogens possess unique molecular structures on their outer surfaces known as ___________.
These molecular structures are recognized by specialized white blood cells called ___________, which then synthesise and release matching antibodies.
Researchers conduct a clinical trial of the new IgE-inhibitor nasal spray on patients with allergic rhinitis.
The patients are randomly assigned to two groups:
They record the mean number of sneezing and congestion episodes per week for each patient before and after the 6-week trial.
The table below shows their results.
| Treatment | Mean number of weekly episodes per patient before treatment | Mean number of weekly episodes per patient after treatment | Percentage decrease in weekly episodes per patient |
|---|---|---|---|
| IgE-inhibitor spray | 18.0 | 4.5 | 75.0% |
| Placebo spray | 18.0 | 13.5 | 25.0% |
The placebo group does not receive the active IgE-inhibitor.
Suggest why this group is included in the clinical trial.
The total number of weekly sneezing and congestion episodes for all patients in the placebo group after the 6-week treatment was 1053.
The mean number of weekly episodes per patient in this group after treatment was 13.5.
Calculate the total number of patients in the placebo group.
Explain why it is important that independent scientists repeat this clinical trial.