Ig-like Molecules Research Articles

The human LT system: III. Characterization of a high molecular weight LT class (complex) composed of the various smaller MW LT classes and subclasses in association with Ig-like molecules

Cytotoxic activity (lymphotoxin (LT)) present in supernatants from lectin stimulated human lymphocytes in vitro is composed of a heterogeneous system of biological macromolecules which can be separated into multiple classes and subclasses on the basis of their molecular weight and charge. These studies further characterize a large molecular weight human LT class, termed complex (MW >200,000 d), which elutes in the void volume off Sephadex G-150 or Ultrogel AcA 44. Immunological studies on the complex, employing various rabbit anti-LT class and subclass antisera, revealed this material is a macromolecular assemblage of the smaller MW α, β, γ LT classes and subclasses. Furthermore, the reactivity of this material with anti-human Fab′ 2 (IgG) indicates these smaller molecular weight LT components can associate with immunoglobulin or Ig-like molecules. The materials present in the LT complex class appear to be noncovalently associated, since conditions of high ionic strength dissociate certain small MW LT components, while low ionic strength buffers may cause these components to reaggregate with the complex. When subjected to velocity sedimentation on sucrose gradients or gel filtration on Ultrogel AcA 22, LT complex activity elutes as several discrete peaks of activity in the 200,000 to 1,000,000 MW range. These findings suggest the concept that LT molecules can form discrete and specific macromolecular structures which contain the smaller MW LT classes. Moreover, these structures can also associate with immunoglobulin-like molecules to form secondary LT-Ig complexes. This may have important biological significance in explaining how nonspecific cell toxins could play a role in specific or nonspecific cell lytic reactions in vitro.

Cell surface immunoglobulins of thymus and spleen lymphocytes in urodele amphibian Pleurodeles waltlii (Salamandridae).

Immunoglobulins associated with the surface of lymphocytes were first described in mammals (1, 2, 3) and then extensively studied. These membrane immunoglobulins are of special importance for the search for recognition mechanisms and cellular cooperation during the immune response. Mammalian B lymphocytes are known to carry membrane Ig; on the other hand, these molecules are not detected on T lymphocytes using classic immunofluorescence techniques except in some cases (4). More sophisticated techniques have to be used in this case, and the data are still conflicting (5, 6). Nevertheless, the presence of Ig-like molecules on mammalian thymocytes seems to have been confirmed (7, 8).KeywordsSplenic LymphocyteSpleen LymphocyteSplenic CellThymic LymphocyteMembrane FluorescenceThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.