Antiserums for immunofluorescent enumeration of human T lymphocytes utilizing fluoresceinated staphylococcal protein A

Five lots (100 ml or more) of heterologous antiserums specific for human T lymphocytes were prepared using human or Rhesus monkey thymocytes as immunogens. After appropriate adsorptions, these antiserums reacted by immunofluorescence with 68% of human peripheral blood mononuclear cells and 98% of human thymocytes, with E-rosette--positive cells but not with EAC-rosette--positive cells or five human B-lymphoblastoid-cell lines. Blocking experiments showed that Rhesus monkey thymocytes share thymic antigenic determinant(s) with humans. E-rosette receptors modulated independently from T-cell heteroantigens. Non-E--rosetting neoplastic T cells were identified in several patients with lymphoproliferative malignancies. Applying both the E-rosette assay and the anti-T-cell serum provides a better method of defining the biologic properties of normal and neoplastic T lymphocytes. Standardization of immunofluorescent conjugates for human T- or B-cell enumeration is simplified if large lots of well-characterized antiserums are available.

Radioimmunoassay for quantitation of antibodies to alphaviruses with staphylococcal protein A

A radioimmunoassay (RIA) procedure is described for measuring antibodies to alphaviruses in human and other mammalian sera. The test employed protein Abearing Staphylococcus aureus as a solid-phase immunoadsorbent for (3)H-labeled viruses complexed with immunoglobulin G. Using antibodies produced in humans and guinea pigs, the RIA procedure clearly differentiated among antibodies to Venezuelan, western, and eastern equine encephalomyelitis viruses. Sensitivity of the RIA depended on the concentrations of labeled viruses employed. The dilution of serum that effected binding of 50% of the (3)H-labeled virus (determined by probit analysis) was consistently higher than the neutralizing antibody titer determined by a conventional plaque reduction neutralization test using 80% plaque reduction end points. In addition, sera from 73 individuals were screened for seroconversion following live attenuated Venezuelan equine encephalomyelitis virus vaccine (strain TC-83) inoculation, by RIA using a single serum dilution (1:80); results were identical with seroconversions identified by plaque reduction neutralization test. Hyperimmune Venezuelan equine encephalomyelitis virus sera from a number of mammalian species were successfully titrated by RIA; the species tested were human, guinea pig, white rat, rabbit, burro, dog, monkey, sheep, and cotton rat. The protein A-mediated RIA is a rapid, sensitive, specific, and precise serological tool for measuring antibodies to surface antigens of alphaviruses, and should allow the subsequent development of a competitive binding RIA to measure antigenic potency of inactivated alphavirus vaccines.

The immunogloblin nature of nephritic factor (NeF)

NeF was shown to be antigenically and structurally similar to IgG by the following experiments: (1) NeF activity in serum was absorbed by and, under acid conditions, could be eluted from (a) anti-myeloma IgG antibody coupled to Sepharose and (b) protein A-Sepharose. (2) Purified NeF could bind to anit-myeloma IgG-Sepharose and could be eluted with acid, and this binding was blocked by myeloma IgG. (3) An antibody to beta2, microglobulin, showing strong cross-reactivity with normal IgG, bound NeF activity before, but not after, absorption of the antiserum with IgG. (4) Sepharose-coupled antibodies to NeF could bind activity which was recovered in the acid eluate. This binding capacity was lost after absorption of the antibody with normal and myeloma IgG. (5) Structural similarity was demonstrated by pepsin and papain digestion, which resulted in NeF activity eluting with F(ab')2 and Fab fragments from protein A-Sepharose and Sephadex G-150. (6) Autoradiography of PAGE-SDS of 125I-labelled NeF eluted from EA43bBb cells showed that NeF had a larger H chain than normal IgG, suggesting that NeF might be an abnormal IgG molecule.

Method for rapid detection of group B streptococci by coagglutination

A quick and reliable technique for the identification of group B streptococci has been developed. The method requires no elaborate equipment or expensive reagents and can be used to detect the group B organisms in mixed broth cultures or to identify suspect colonies selected from agar plates. The method is a coagglutination technique in which 1 drop of specifically sensitized protein A-containing Staphylococcus aureus is mixed with 1 drop of supernatant of an actively growing culture. The soluble group-specific carbohydrate substance of the group B streptococci reacts with the staph particles to produce agglutination that is macroscopically readable. One colony of group B streptococci taken from an agar plate and inoculated into Todd-Hewitt broth will give a positive reaction within 6 h of incubation; with a larger inoculum, the positive reaction occurs within a shorter period. The method was applied for detection of group B streptococci in mixed broth cultures. In laboratory studies involving random mixtures of organisms, 59.3% of positive cultures were detected within the first 8 h of incubation, and 71.7% were found within 24 h. In clinical studies with mixed broth cultures grown directly from vaginal swabs, 78.6% of the positive cultures were detected within the first 8 h of incubation, and 92.9% were found within 24 h.

[Diphtheria toxin titration using "Staphylococcus aureus" protein A (author's transl)]

The antigen-antibody reaction between diphtheria toxin and its corresponding IgG antibody may be visualized if IgG are adsorbed on the surface of S. aureus cells carrying protein A (SpA). If enough antigen is mixed with SpA--IgG, a visible agglutination occurs. On a glass slide, a rapid test can detect 0.3 Lf/ml toxin. If the mixtures are incubated overnight at 37 degrees C, the highest dilution of toxin producing agglutination is 0.01 to 0.02 Lf/ml for a given batch of toxin. The sensitivities of this or of the biological titration using the lethal effect on guinea-pigs are the same. The high sensitivity of the skin reaction was however not approached.

An indirect immunofluorescent antibody test for determination of Rubella virus specific IgM antibodies. Elimination of secondary IgM rheumatoid factor staining after absorption of serum IgG with Staphylococcal protein A

Absorption of sera with protein A rich staphylococci eliminated unwanted secondary IgM staining caused by rheumatoid factors in the indirect immunofluorescence test for rubella virus antibodies. The absorption did not lower the sensitivity for IgM rubella antibodies as compared with the haemagglutination inhibition test on the IgM serum fractions obtained by ultracentrifugation.

Herpes gestationis: studies on the binding characteristics, activity and pathogenetic significance of the complement-fixing factor

The sera of seven out of eight patients with Herpes gestationis contained a factor which fixed C3 but not detectable amounts of immunoglobulin (Ig) on the basement membrane zone (BMZ) of normal human skin. Using C2-deficient human serum and C4-deficient guinea-pig serum, fixation was shown to be dependent upon activation of the classical pathway, and chromatography and immunoabsorption studies indicated the H. gestationis factor to be an IgG immunoglobulin. In all seven sera the H. gestationis factor bound to, and could be eluted from, the eluate of staphylococcal protein A. Although the H. gestationis factor failed to block staining of human sera by a FITC-conjugated antibody prepared from bullous pemphigoid (BP) serum, complement fixation by five out of seven sera of patients with H. gestationis was blocked using F(ab')2 of IgG prepared from pooled BP serum. In a single patient rapid resolution of lesions followed plasma exchange on two separate occasions, indicating the pathogenetic importance of humoral factors in this disease.

Separation of IgE from IgG subclasses using staphylococcal protein A

When human serum was passed through a column of insolubilised protein A, IgE was not removed, but IgG sublasses 1,2 and 4 were retained. Protein A did not show a similar selectivity in its interaction with rat immunoglobulins. The separation of human IgE from the bulk of the IgG was used to examine the effect of IgG on IgE-mediated sensitization of lung tissue for histamine reslease. Removal of IgG led to a significant increase in histamine release, suggesting that homocytotropic IgG competes with IgE, for binding sites on mast cells.

A radioimmunoassay for tetanus antibodies using protein A - containing Staphylococcus aureus

To measure tetanus antibodies a trace amount of 125I-labeled tetanus toxin is mixed with appropriate dilutions of human serum or blood. The labeled antigen-antibody complexes are adsorbed to heat-killed staphylococci (Cowan I) via their surface protein A. The radioactivity of the washed solid phase is a function of the initial antibody concentration. The test allows the measurement of 6 X 10(-0) U of tetanus antitoxin in a volume of 0.03 ml. In order to avoid possible interferences, serum has to be diluted 20-fold before use. Taking that into account, the real border limit of sensitivity is 4 X 10(-3) U/ml serum. Antibodies may be measured in serum, in plasma, and even in heparinized blood. As to its sensitivity, the test compares well with the toxin neutralization procedure. It is superior to the previous radioimmunologic, enzymoimmunologic, and hemagglutination techniques with respect to sensitivity and reproducibility. It reflects the values obtained in the toxin neutralization test better than the other in vitro procedures, as shown by parallel assays of 17 sera.

Isolation of soluble immune complexes by affinity chromatography using staphylococcal protein A--Sepharose as substrate

This report describes a technique for the general isolation of immune complexes, based on a combination of gel filtration and affinity chromatography. The first step is the preparation of a globulin-enriched fraction by precipitation with ammonium sulfate at 50% saturation, or of an immune-complex-enriched fraction by precipitation with 5% polyethylene glycol 6000. The enriched fraction is then subfractionated by gel filtration in Ultrogel AcA 34. The immune complexes elute close to the void volume in the macroglobulin peak, separated from monomeric IgG molecules. This peak (sometimes subdivided into two fractions) is then submitted to affinity chromatography on a protein A--Sepharose cooumn. Most immune complexes contain IgG molecules and therefore bind to the column. Almost no protein is bound when normal serum is fractionated according to this method, and no immunoglobulins are detectable in the acid-eluted fraction from the protein A--Sepharose column. In two patients with soluble immune complexes in their sera we eluted immunoglobulin-containing fractions from the column; in one, these fractions had high rheumatoid factor titers; and in the second, with a clinical diagnosis of systemic lupus erythematosus, a similar fraction contained RNA.

“CELL-WALL PROTEIN A” OF PSEUDOMONAS AERUGINOSA AND ITS RELATIONSHIP TO “ORIGINAL ENDOTOXIN PROTEIN”

Homma, J. Yuzuru (University of Tokyo, Tokyo, Japan), and Nachiko Suzuki . “Cell-wall protein A” of Pseudomonas aeruginosa and its relationship to “original endotoxin protein.” J. Bacteriol. 87: 630–640. 1964.—To compare the properties of two kinds of proteins, one obtained from the cell wall of Pseudomonas aeruginosa and the other from the endotoxin in the autolysate, the proteins were purified to such an extent that they were proved to be homogeneous by zone electrophoretic and ultracentrifugal analyses. Although there were some differences between the two in such values as nitrogen and phosphorus contents and sedimentation constants, their protein portions were found similar to each other in the ratio of amino acid compositions. It was proved serologically that the two proteins possessed a common specific antigen. They were found to be the same in their potencies in eliciting the Shwartzman phenomenon and pyrogenic reaction. The results of pyocine tests with various sensitive strains revealed that, against the sensitive strains, the spectra of both proteins were almost the same. Their pyocine activities were destroyed through digestion by protease, trypsin, and Nagarse. Either of the rabbit antisera against the two proteins could neutralize pyocine activities of both proteins. Serum-absorption tests proved that the pyocine-neutralizing antibodies of both antisera could be completely absorbed with each of the proteins. Under appropriate conditions, their pyocine activities were masked partially in vitro by the lipopolysaccharde of the endotoxin.