Low molecular weight Ia antigens in normal mouse serum

Increased serum concentration of soluble HLA-DR antigens in HIV infection and following transplantation

HLA class I and class II antigens circulate in serum as soluble molecules. Increased concentrations of soluble HLA class I molecules have been demonstrated in viral diseases, in rejection episodes following organ transplantation and in graft versus host disease. To explore the possibility of a variation of the serum concentrations of soluble HLA class II molecules in the same pathologic conditions we developed a double determinant immune assay that detects whole soluble HLA-DR molecules (sHLA-DR). The mean level of sHLA-DR antigens in sera from 23 healthy individuals was 0.64 +/- 0.72 microgram/ml. Elevated serum concentrations of sHLA-DR molecules were detected in sera from HIV infected patients in CDC2/3 and in CDC4 C1 stages (2.0 +/- 1.7 micrograms/ml and 4.6 +/- 1.7 micrograms/ml, respectively), in sera from patients affected by acute rejection after liver transplantation (5.3 +/- 3.7 micrograms/ml) and in sera from patients affected by severe acute graft versus host disease following bone marrow transplantation (8.8 +/- 3.1 micrograms/ml). The increase of sHLA-DR molecules in these sera significantly correlated with the elevation of soluble HLA class I antigens (P = 0.0004). The reported data suggest that both soluble HLA class I and class II molecules serum levels increase during viral infections and strong immune reactions and could suggest the involvement of these molecules in immunoregulation.

Quantitation of soluble HLA class II molecules by an enzyme-linked immunosorbent assay

In order to quantify soluble HLA-DR,DQ,DP molecules (sHLA-RQP) an enzyme-linked immunosorbent assay was developed utilizing two monoclonal antibodies specific for HLA-DR,DP (Tü35) and HLA-DQ (Tü22) gene products, respectively. Highly purified HLA class II molecules isolated from a lymphoblastoid cell line were used for calculation of exact sHLA-RQP protein values. Circadian variations of sHLA-RQP plasma levels were studied in 7 healthy probands showing no significant deviations; measurements in 4 probands at intervals between 4 and 6 weeks revealed that sHLA-RQP levels remain relatively stable. The population analysis of 209 unrelated, HLA-typed healthy donors resulted in an average protein concentration of 1.53 +/- 2.44 micrograms/ml plasma for sHLA-RQP. Four out of 209 probands (= 1.9%) had no detectable sHLA-RQP. Significant associations of high or low sHLA-RQP levels to particular HLA-DR or -DQ specificities were not observed. However, plasma derived from HLA-DR9 positive had the highest and from HLA-DR8 positive donors the lowest mean sHLA-RQP values. By comparing HLA identical with two-haplotype-different siblings we found no evidence that sHLA-RQP plasma levels are under genetic control of the HLA complex or closely linked genes. Furthermore, soluble HLA class I plasma concentrations in 100 probands analyzed showed no correlation to those of sHLA-RQP.

Class I and class II regions of the major histocompatibility complex both contribute to individual odors in congenic inbred strains of rats

The major histocompatibility complex (MHC) of the rat has three regions--A (class I), B/D (class II), and C/E (class I)--and congenic strains are available which differ in each of these regions. We used the habituation-dishabituation procedure to examine the ability of PVG-RT1u male rats to discriminate between the urinary odors of congenic rat strains which differ genetically only at certain individual regions of the MHC. The results of five experiments indicate that discrimination can be made between urine from rats which differ in all three regions of the MHC (PVG vs. PVG-RT1av1 donors), only in the class I A region (PVG vs. PVG.R1 donors), only in the class I C/E region (PVG.R19 vs. PVG-RT1av1 donors), only in the class II B/D region (PVG.R1 vs. PVG.R19 donors), and in all regions except the classical class IA locus (PVG-RT1av1 vs. PVG.R1 donors). These results indicate that all of the MHC regions may contribute to the individual odors of rats.

Production of monoclonal antibodies to serum antigens in colorectal carcinoma

Two monoclonal antibodies (mAb) to colorectal cancer were produced using a novel immunization technique. This involved immunizing mice with whole serum obtained from patients with cancer of the colon (three with metastatic disease) and resulted in antibodies which were reactive with colonic tumor tissue by immunoperoxidase testing. Two mAbs (O-1, I-1) were isolated which were non-reactive with normal tissue and with tissues obtained from subjects with benign disease but were reactive with 34/50 (formalin-fixed) colon carcinoma specimens. Further testing on cell lines and other malignant tumors suggested both mAbs detect carcinoembryonic antigen (CEA) as their reactivities were similar to a known anti-CEA antibody, and they reacted with CEA in a solid-phase radioimmunoassay. The two mAbs were found to react with the same or closely associated epitopes on CEA by competitive tests. As the anti-CEA antibodies were made to serum (rather than tissue) CEA, it was possible that unique, highly specific mAb has been produced, particularly as there was a selective reaction of the mAbs for malignant but not normal tissues. A serum test with mAb I-1 was developed which detected raised serum CEA levels in 3/24 patients with benign colonic lesions, 7/19 patients with pancreatic cancer, 5/25 patients with colonic cancer but not in 20 normal individuals. There was direct correlation between these results and a commercially available CEA test kit.

Stimulator requirements for primed alloreactive T cells: macrophages and dendritic cells activate T cells across all genetic disparities

The cellular requirements for stimulating primed alloreactive T cells have been investigated. In vitro-primed secondary alloreactive cells, long-term lines, and Ly 1+2- noncytolytic clones which reacted with allo-H-2K, D, or Mls (M locus) antigens were tested. The data indicated that a specialized antigen-presenting cell such as a macrophage or a dendritic cell was required for stimulating primed alloreactive cells across all the genetic disparities tested. B and T lymphocytes were ineffective stimulators. The stimulator requirement for secondary and Ly 1+2- clone responses was heterogeneous, since both macrophages and dendritic cells were effective stimulators. Thus, the allostimulator requirement for inducing proliferation and mediator secretion by the primed T-cell populations closely paralleled the requirement for stimulating unprimed populations. The only exception found was the peritoneal washout population, which did not stimulate a primary response but did stimulate secondary responses. The failure of peritoneal macrophages to stimulate a primary response was shown to be due to an inhibitory pathway which did not occur when the responding population was alloantigen primed.

Latex bead rosetting method for cell surface antigens

Polystyrene latex beads coupled with anti-Ig can be used to detect the binding of specific antibodies to target cells. The optimal conditions for coupling anti-Ig to beads are described. This method is as sensitive as red cell rosetting and has the advantages that coupling is simple and the coated beads stable.

A sensitive and quantitative fluorescence assay for cell surface antigens

A procedure is described for the assay of cell surface antigens based on quantitative fluorometry. Fluorescent immunospheres are coupled with sheep anti-mouse immunoglobulins or Protein A and used to detect specific antibody bound to target cells. The fluorescent sphere assay described here offers 16--128-fold greater sensitivity than complement mediated lysis or Protein A radioimmune assays and comparable sensitivity to rosetting assays. In addition, the assay is simple to perform, uses commercially available reagents and is completely objective in that a common laboratory fluorometer is used to obtain fluorescence measurements.

Demonstration of carbohydrate- and protein determined Ia antigens by monoclonal antibodies

Ten monoclonal alloantibodies were examined by submitting each antibody to five independent tests in order to determine whether they reacted primarily with the glycoprotein or glycolipid class of Ia antigens. The tests employed were as follows: (1) the ability to participate an Ia-like protein from the cell surface as detected by SDS-PAGE; (2) inhibition by protein-Ia extracts free of CHO-Ia; (3) inhibition by CHO-Ia extracts free of protein-Ia; (4) neuraminidase sensitivity of the antigen and (5) inhibition by simple sugars. Using these tests, three of the ten monoclonal antibodies were shown to recognize a CHO-Ia antigen while seven recognized the protein class of Ia antigens. The three CHO-Ia-specific monoclonal antibodies recognized Ia specificities 2, 9 and 17. Monoclonal antibodies recognizing protein-defined Ia.2 and 17 specificities were also characterized. These results imply that some Ia specificities, as defined by genetic testing, can occur both as carbohydrate-defined and protein-defined determinants.--Sugar inhibition studies showed that CHO-Ia.2 has D-glucosamine as its immunodominant sugar while CHO-Ia.17 shows preference for a beta-linked galactose. Furthermore, studies with neuraminidase demonstrated that sialic acid plays a role in the antigenic determinants of CHO-Ia.9 and CHO-Ia.17. Finally, it is noteworthy that CHO-Ia.2, the private specificity of the k haplotype, appears to be expressed only on cells and not in serum. These studies clearly demonstrate the existence of the two Ia antigen classes and emphasize the complexity of the murine I region.

Biochemistry of major human histocompatibility antigens

The major histocompatibility region, designated HLA in man and H-2 in the mouse, controls the expression of at least three groups of gene product - serum complement components and two sets of highly polymorphic cell-surface antigens, the so called histocompatibility antigens. In this review Michael Owen and Michael Crumpton describe some recent insights into the biochemical structure of HLA antigens.

Major histocompatibility gene complex (MHC)-coded determinants on antigen-specific suppressor factor for delayed-type hypersensitivity and surface phenotypes of cells producing the factor

Antigen-specific suppressor factor for delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) was obtained by incubating in vitro spleen cells from CBA mice (H-2k) injected intravenously 3 days previously with 1 x 10(9) SRBC. The suppressor factor was characterized for major histocompatibility gene complex (MHC)-coded antigenic determinants by passing the factor through immunosorbents coupled with appropriate alloantisera. The suppressor factor was absorbed by anti-H-2k, anti-Iak and anti-I-Jk immunosorbents but was not retained by anti-Ias, anti-I-Js, anti-I-Ak, anti-I-E/Ck or anti-H-2Kk immunosorbents. In addition, the factor bound to an immunosorbent coupled with rabbit antibodies against carbohydrate-defined Ia antigens. Furthermore, the suppressive activity that was absorbed was quantitatively recovered in the acid eluates from the immunosorbents. Treatment of the spleen cells with anti-Lyt-1.1 antiserum and complement completely abrogated their ability to elaborate the suppressor factor in vitro. In contrast, treatment with anti-Lyt-2.1 or anti-Iak antiserum and complement had no effect. Thus, it appears that the suppressor factor for DTH to SRBC bears I-J subregion-coded determinants, and its production is dependent on cells which have the Lyt-1+,2- and Ia- phenotype.

Serological analysis of antigen-specific helper factors specific for poly-L(Tyr, Glu)-poly-DLAla--poly-LLys [(T, G)-A--L] and L Glu60-LAla30-LTyr10 (GAT)

In vitro prepared antigen-specific helper factors reactive to the synthetic polypeptide antigens poly-L(Tyr, Glu)-poly-DLAla--poly-LLys [(T, G)-A--L] or LGlu60-LAla30-LTyr10 (GAT) and bearing Ia determinants were analyzed serologically to determine the nature of the Ia determinants they expressed. I subregion-specific mouse anti-Ia antisera were used, and showed that (T, G)-A--L-specific helper factor (HF) contains I-A subregion-controlled determinants, whereas GAT-specific HF carries I-J subregion-controlled antigens. This unexptected finding was confirmed in both the H-2k and H-2 b haplotypes, using a variety of anti-I-J antisera. Rabbit anti-Ia antisera also reacted with both HF which raised the possibility that the Ia determinants on HF may be carbohydrate in nature. The fact that HF has a low molecular weight and yet contains Ia determinants, antigen-binding capacity and idiotypic markers is compatible with this interpretation.

Regulation of IgE antibody production by serum molecules. VI: Preliminary biochemical and immunological characterization of serum molecules active in suppressing IgE antibody production

Molecules present in the serum and ascites fluids of low IgE responder mice previously inoculated with complete Freund's adjuvant have been analyzed in terms of certain biochemical and immunological characteristics. These studies demonstrate that the active molecules, termed "suppressive factors of allergy" (SFA), are (1) nondialyzable, (2) not associated with low-density or high-density lipoproteins, (3) heat stable, (4) precipitable by ammonium sulfate, and (5) approximately 150,000 daltons in molecular size. Studies with immunoadsorbents prepared from various antisera indicate that the suppressive molecules are (1) not immunoglobulin in nature, (2) not reactive with specific anti-H-2 alloantibodies, but (3) reactive with anti-beta 2m antibodies as well as (4) heterologous antisera raised against CFA-immune mouse serum.

A sensitive rosetting method for detecting subpopulations of lymphocytes which react with alloantisera

A procedure is described for directly estimating the proportion of mouse lymphoid cell suspensions which react with alloantisera. The method entails reacting Ig-capped lymphoid cells with alloantisera, and then assessing the uptake of alloantibodies by rosetting the lymphocytes with SRBC coated with sheep IgG specific for mouse Ig. This rosetting procedure was found to be generally more sensitive than the conventional dye exclusion microcytotoxicity test for detecting the binding of alloantibodies to lymphocytes. Furthermore, the rosette method has the advantage that, unlike the complement lysis technique, it has a low and reproducible background and lymphocyte subpopulations which react with alloantisera can be isolated.