Final answer:
The true statement is 'c. The four cardinal signs of inflammation are erythema (redness), calor (warmth), dolor (pain) and swelling (edema).' Antibodies consist of two light and two heavy chains, and the class of antibody primarily related to allergies is IgE, not IgA.
Step-by-step explanation:
The statement that is true is 'c. The four cardinal signs of inflammation are erythema (redness), calor (warmth), dolor (pain) and swelling (edema)'. Antibodies, or immunoglobulins, consist of two identical heavy chains and two identical light chains forming a Y-shaped structure. Therefore, statement 'a' is incorrect as antibodies comprise of two light and two heavy chains, not one of each.
Regarding autoimmune disorders, they are characterized by the body's immune system attacking its own tissues, but not necessarily by a reduction in the number of antibodies, making statement 'b' incorrect. In many autoimmune disorders, the number of antibodies may be normal or even elevated, depending on the specific condition and immune response.
Statement 'd' is incorrect because the class of antibody most closely associated with allergic reactions is IgE, not IgA. While IgA is indeed found in mucous membranes, IgE's role in the immune system is strongly linked to the promotion of allergic reactions and hypersensitivity by causing mast cells and basophils to release histamine and other mediators.