Final answer:
The term spelled correctly is 'immunoglobulin'. These are critical components of the immune system, with IgG being the most abundant in human blood, responsible for combating diseases.
Step-by-step explanation:
The term that is spelled correctly is immunoglobulin. Immunoglobulins, also known as antibodies, are glycoproteins in the immune system that play a crucial role in identifying and neutralizing foreign objects like bacteria and viruses. Among the different classes of immunoglobulins present in the human body, IgG is found in the highest concentration in the blood and is primarily responsible for fighting diseases by being highly specific to the antigen. The structure of immunoglobulins is complex, involving various chains, with the proportion of kappa (k) and lambda (λ) light chains differing among species. In humans, 65% of light chains are kappa and 35% are lambda. Immunoglobulins are secreted by B-cells and are essential for the immune response against pathogens.