Final answer:
Light chains have two isotypes: kappa and lambda. An antibody cannot have both isotypes; it must have two light chains of the same type. The human ratio of kappa to lambda light chains is approximately 2:1.
Step-by-step explanation:
Yes, light chains do have isotypes. Specifically, there are two different isotypes: kappa (κ) and lambda (λ). Each immunoglobulin light chain is composed of a variable domain and a constant domain, with the kappa type consisting of 214 amino acids. Unlike heavy chains, which can have gamma (γ), alpha (α), mu (μ), epsilon (ε), and delta (δ) isotypes corresponding to the different classes of antibodies (IgG, IgA, IgM, IgE, IgD), the light chain isotypes do not determine the class of antibody.
It is important to note that while an antibody can have either kappa or lambda light chains, it cannot have both; within the same antibody molecule, the two light chains must be of the same type. Furthermore, in humans, approximately 65% of light chains are kappa and 35% are lambda. This ratio varies from species to species, with the proportion of each light chain type influencing the overall immunoglobulin function.