Give two types of cell that can stimulate an immune response.

1

2

An autoimmune disease causes the immune system to attack healthy body tissues.

Scientists investigated the immune responses of healthy mice and mice with autoimmune disease.

The chemical OXA causes an immune response in mice and can make their skin swell. Mice had olive oil applied to their left ear and OXA in olive oil applied to their right ear.

The immune response was recorded in two ways: • the cellular response by measuring the mean increase in ear thickness 24 hours after exposure to OXA • the humoral response by measuring the mean concentration of anti-OXA antibody in blood 14 days after exposure to OXA.

Table 2 shows the results of this investigation. The values in the brackets show ± 2 standard deviations. A value of ± 2 standard deviations from the mean includes over 95% of the data.

Suggest and explain one reason why olive oil was applied to the left ear of the mice.

Plot a suitable graph for mean increase in ear thickness for each group of mice in Table 2.

Include the data for ± 2 standard deviations on your graph.

What can you conclude about the effects of autoimmune disease on the cellular response and the humoral response in male and female mice?

Use the data to justify your conclusions.

Some studies have shown that in humans, oestrogen has the opposite effect on two different autoimmune diseases. Oestrogen: • accelerates the progression of systemic lupus erythematosus (SLE) • prevents the progression of rheumatoid arthritis (RA).

The scientists investigated the effect of oestrogen on the immune response in healthy mice and mice with autoimmune disease.

Table 3 shows the scientists' results.

A student studying these data made the following conclusions.

1. In humans, SLE is caused by an overproduction of antibodies. 2. In humans, RA is caused by an overproduction of cytotoxic T cells (TC cells).

Evaluate the student's conclusions.

In mice, one type of autoimmune disease is inherited as a dominant allele. Would the Hardy–Weinberg principle hold true for a population of mice, some of which had this autoimmune disease?

Explain your answer.