Immunochemical analysis of IgG subclasses and IgM in South American camelids

Abstract Antibodies are glycoproteins comprising two heavy and two light chains. Surprisingly, all members of the family Camelidae possess a fraction of antibodies devoid of both light chains and the first constant domain (CH 1 ). These kinds of antibodies are known as heavy chain antibodies (HCAbs). There are three subclasses of IgG in dromedaries, namely IgG 1 , IgG 2 and IgG 3 of which, IgG 2 and IgG 3 are of the HCAbs type. In the present work, the different IgG isotypes from guanaco ( Lama guanicoe ), llama ( Lama glama ) and vicuna ( Vicugna vicugna ) were purified and characterized. Interestingly, it was found that IgM was capable of binding to protein A. The different subclasses of immunoglobulins were also assayed for their ability to fix complement. Both IgG 1 and the total serum were able to fix complement, whereas IgG 2 and IgG 3 fixed complement even in the absence of antigen.