Question

Dr. O'Dell continued. "Low TSH levels should result in low thyroxin levels, not the reverse. Something seems to be stimulating the thyroid in the absence of TSH. When I saw your results, I spoke to Dr. Rasam and he suggested a special ELISA test on the blood sample I collected from you. The ELISA result indicates that Carrie shows early signs of Graves disease." Both Carrie and Robert looked confused. "Carrie, a subset of your immune system antibodies is mistakenly attacking your thyroid gland, causing an increase in hormone production. Common symptoms include insomnia, anxiety, fatigue, heat sensitivity, weight loss, and increased sweating. Your hair might get brittle, and your menstrual cycle might change." Carrie nodded. "I've had all those symptoms." "But this Graves disease can be cured, right?" asked Robert, holding Carrie's hand tightly. "It's treatable, yes, but this autoimmunity is a lifelong problem that has to be carefully managed to avoid symptoms such as eye swelling or bulging often seen in Graves patients, as well as other complications."

Consider the immunological involvement in this case, and the time frame over which it has occurred.
(a) Which antibody (Ig) class was produced first in this sequence of events?
(b) Which class is most likely involved in an ongoing autoimmunity situation? Return to your thyroid-pituitary diagram.

Answer 1

Answer: a) IgM

b) IgG

Step-by-step explanation:

Autoimmunity occurs when the body sees it's cells as foreign antigens and begins to form antibodies to fight them. For example, Graves' disease is an autoimmune disorder, in which the body produces antibodies to the receptor for thyroid-stimulating hormone and this binding causes chronic stimulation of the receptor which in turn causes hyperthyroidism.

THERE ARE FIVE CLASSES OF ANTIBODIES (IMMUNOGLOBULINS):

The first class, called IgM, is the major component of the primary antibody response in adult humans and is the first antibody to appear in the immune reaction.

The principal antibody of the secondary immune response is IgG. This antibody is the most common in the bloodstream.

The third class of antibody is IgA. This antibody is found in external secretions.

The fourth class of antibody, IgD, is found in extremely small quantities in the serum.

The final kind of antibody, IgE, occurs in minute concentrations in the serum and is important in hypersensitivity reactions.