Isotypic

Isotypic is an adjective used in the sciences to describe two or more entities that share the same type or form. The term combines iso- equal and -typic from type, and its precise meaning varies by field, but generally denotes structural or functional similarity within a class while allowing differences in composition or origin.

In immunology, isotype refers to the class of an antibody defined by its constant region of the heavy chain: IgA, IgD, IgE, IgG, and IgM, among others. Isotypic differences govern distribution and effector functions (e.g., complement activation, placental transfer). B cells can switch from one isotype to another in a process called class-switch recombination, changing antibody function without altering antigen specificity. An isotypic antibody response describes production of antibodies of a particular isotype across a response.

In crystallography and solid-state chemistry, isotypic compounds have the same crystal structure or structure type, and belong to the same structure family, though their chemical compositions differ. Substitution of different cations or anions can yield an isotypic series, preserving lattice symmetry and coordination environment.

In summary, isotypic is used across disciplines to denote sameness of type at a higher level, with domain-specific details about what is considered the type and what variations are allowed.