Direct radiation damage is confined to a single polypeptide in rabbit immunoglobulin G.

Frozen rabbit immunoglobulin G was exposed to high-energy electrons. The surviving polypeptide subunits were determined and analyzed by radiation target analysis. Each subunit was independently damaged by radiation whether or not they were bound by disulfide bridges to other subunits, demonstrating that in IgG radiation-deposited energy did not travel across disulfide bonds.

Spontaneous helper factor production by nonadherent rabbit lymphoid cells and its feedback regulation by adherent cells.

Normal, unstimulated rabbit lymphoid cells, when depleted of adherent cells, produced soluble helper factor activity that augmented antibody formation by rabbit spleen cells primed against sheep red blood cells (SRBC). Adherent cells inhibited the production of the helper factor by nonadherent cells via a soluble product. Thus unseparated (adherent cell-containing) appendix, lymph node, and spleen cell cultures did not produce the helper factor. On the other hand, the activity of the helper factor required the presence of adherent cells in the assay cultures. Peritoneal exudate cells, predominantly esterase positive, also inhibited the production of the helper factor if they were first exposed to the helper factor-containing culture supernatant. These results imply that a helper factor may participate in the feedback regulation of its own production via an adherent cell population.

Effect of alcohol on the integrity of the intestinal epithelium.

The absorption of macromolecules from the small intestine of rats was studied in terms of the amount of peroxidase activity that appeared in thoracic duct lymph after a 10 mg dose of horseradish peroxidase had been injected directly into the lumen of the duodenum. When the horseradish peroxidase was injected as a solution in saline no peroxidase activity was detected in the lymph. When ethyl alcohol was included in the dose at final concentrations of 12.5-16% the flow rate of the lymph increased markedly for an hour or so and during this time peroxidase activity was detected in the lymph. An electronmicroscope study of the duodenal epithelium that had been exposed to alcoholic solutions of horseradish peroxidase showed that the enzyme had penetrated between the enterocytes. It was concluded that the presence in the intestine of substantial amounts of alcohol temporarily destabilises the intercellular junctions of the epithelium and thus promotes the absorption of materials which are normally excluded.

An inverse relationship between serum immunoglobulin-G and intellectual functioning.

Serum immunoglobulin levels for IgA, IgE, IgG, and IgM were measured in 13 institutionalized, profoundly mentally retarded individuals and for 20 retarded and 29 intellectually average noninstitutionalized individuals. A significant elevation in IgG was observed for the retarded groups as compared with the intellectually average group. There was a significant inverse relationship between IgG and level of intellectual functioning. The elevated IgG is suggestive of the findings with auto-immune diseases and warrants further investigation.

Responsiveness of rabbit spleen and appendix cells to bacterial mitogens.

Rabbit spleen and appendix cells were used to test the mitogenic activity of a commercial lipopolysaccharide (LPS) preparation from Salmonella typhimurium (Difco), a preparation extracted from it, and cell wall preparations from smooth (45/0) and rough (45/20) strains of Brucella abortus. On the basis of [3H]thymidine incorporation ratios (E/C), that is, the incorporation rate among cells treated with the mitogen relative to that of untreated cells, the extracted LPS and both Brucella cell wall preparations, but not the commercial LPS were potent mitogens for rabbit spleen cells. By the same criterion, only the Brucella cell wall preparation produced a significant, but minimally so, response among appendix cells. The weak responsiveness of appendix cells may be more apparent than real, however, and may not imply a difference in intrinsic susceptibility to mitogens by these two populations, because unstimulated appendix cells incorporated thymidine at 10 times the rate of unstimulated spleen cells. Appendix cells, then, may not be susceptible to further stimulation, even by active mitogens. Therefore, the significance of E/C ratios may be equivocal when materials are assayed for mitogenic activity on lymphoid populations whose basal activity is relatively high.

Mitogenic activity of cell wall components from smooth and rough strains of Brucella abortus.

On the basis of [3H]thymidine incorporation by normal mouse spleen cell cultures, cell wall preparations from a smooth (45/0) strain and a rough (45/20) strain of Brucella abortus were strongly mitogenic. On the other hand, none of several subcomponents extracted from the cell wall preparations, including aqueous and phenolic lipopolysaccharides, was active. These results contrast with the marked mitogenic activity of lipopolysaccharides isolated from other gram-negative bacteria such as Salmonella typhimurium.

Development of the rabbit appendix. I. Electron-microscopic observations.

The progressive lymphoepithelial development of the rabbit appendix was examined by light and electron microscopy. At 5 days postnatally, the appendix wall primitively resembles the mature organ but lacks both the discrete lymphoid organization and most cell types. The dome appears to be the first recipient of lymphoid cells. By 18 days the lymphoid nodule has become compartmentalized and lymphoid. The epithelium, although not fully developed, is in contact with the lymphocytes of the dome. The 5-week-old appendix has all the lymphoepithelial components of the adult but lacks the size of the mature organ. At all ages reported, plasma cells and dendritic cells are absent. Bacteria, thought to be essential to appendical lymphoid development, are not apparent at 5 or 18 days. The features common to central or peripheral lymphoid tissues are discussed.

Factors affecting the passive hemagglutination titration: dilution loops, titration trays, vibration, diluents.

Serial dilution with Takatsy loops resulted in exaggerated passive hemagglutination titers with most of the anti-bovine serum albumin sera tested. It appears that certain types of agglutinins adhere to the loop surface and are released only gradually. This adherence, or carry-over effect, was prevented by presoaking loops in gelatin or gelatin-rabbit serum-albumin solutions. Hemolysins did not adhere to loops. In general, hemagglutination reactions performed on plastic trays gave higher titers than those performed in glass test tubes. The quality of the hemagglutination pattern was dependent to a great extent on the type of plastic tray used. As much as a 100-fold difference in titers was obtained depending on the composition of the antiserum diluent. The increase in vibration, in terms of linear displacement (approximately twofold), resulted in an eightfold decrease in titers.