Induction and measurement of in vivo antibody responses.

The capacity of the human immune system to mount an antibody response following in vivo immunization with a protein or polysaccharide antigen is a revealing indication of the overall integrity of both the B and T cell arms of the immune system. As such, in vivo immunization followed by measurement of the antibody response is an appropriate test of immune function in the various acquired and congenital immunodeficiencies and in a host of other conditions affecting the immune system. This unit describes procedures for in vivo immunization and for the measurement of the subsequent immune response using an ELISA technique.

51Cr release assay of antibody-dependent cell-mediated cytotoxicity (ADCC).

Antibody-dependent cell-mediated cytotoxicity (ADCC) is an immunologic cytotoxic effector mechanism that is dependent on the cooperative interaction of humoral and cellular effector elements. This unit describes an assay of ADCC activity that can be used as a test for immunocompetence in effector cells or to test the activity of a monoclonal antibody to mediate ADCC. In this form of cytotoxicity, effector cells with receptors for the Fc portion of immunoglobulin produce target cell lysis by attachment to the Fc portion of antibodies that are bound to target cells via their antigen-combining sites. Therefore, an ADCC assay involves three essential components: labeled target cells, antibodies with specificity for target-cell surface antigens, and effector-cell populations. The basic protocol describes a method of measuring ADCC effector activity in lymphoid cells (peripheral blood mononuclear cells, or PBMC) that employs (51)Cr-labeled target cells. The three components are mixed in microtiter-plate wells and lysis of the target cells is detected by measuring the release of radioactivity into the cell supernatant. Support protocols describe procedures for preparing anti-target cell antiserum and (51)Cr-labeled target cells.

Serum neopterin, beta2-microglobulin, soluble interleukin-2 receptors, and immunoglobulin levels in healthy adolescents.

Serum biomarkers, such as neopterin, beta2-microglobulin (B2M), and soluble interleukin-2 receptors (sIL-2R), are elevated in viral infections, including HIV-1 infection, and in inflammatory conditions, autoimmune disease, and malignancies. For many of these conditions, serum levels correlate with disease activity. Application of these biomarkers in adolescents is limited by a lack of information on the range and determinants of variability (age, sex, race) for serum levels of these important molecules in this age group. To address this question, we analyzed serum samples from a well-characterized heterogeneous population of 111 healthy adolescents. White children had significantly higher serum levels of sIL-2R and IgM and lower levels of IgG (P

Temporal variability in immunological parameters: peripheral blood mononuclear cell subsets, serum immunoglobulins, and soluble markers of immune system activation.

T-cell subsets and soluble factors of immune system activation are increasingly used as biologic markers of disease and predictors of disease progression. For example, changes in CD4 cells and CD4:CD8 ratio, sIL-2R, B2M, neopterin, and IgA have been used in predicting AIDS onset and progression. We examined the temporal variability of T-cell subsets, monocytes, natural killer cells, B cells, immunoglobulins, soluble interleukin-2 receptor (sIL-2R), neopterin, and beta-2 microglobulin (B2M) among 135 adults tested at two time points approximately 3 months apart. The purpose of the study was two-fold: (1) to assess the stability of these measures at two points in time, and (2) to investigate which parameters tend to track together over time, i.e., show significant longitudinal correlation. Mean population values for these immunologic parameters remained remarkably stable over the 3-month period. However, individual subjects exhibited significant temporal variability for many parameters. Unlike observations in patients with AIDS, changes in immunoglobulins and other soluble factors were not significantly correlated with changes in cellular subsets over the same period. However, change in B2M was correlated with change in neopterin (r = .35, p < or = .0001), and change in IgA was correlated with changes in IgG and IgM (r = .44, r = .54, P < or = .001 for both). Characterizing this temporal variability in a healthy population provides important information for researchers applying these tests in clinical and epidemiological studies.

Release of sIL-2R alpha from and activation of native human peripheral blood mononuclear cells by recombinant IL-15.

The cytokine interleukin (IL)-15 shares several activities with IL-2. Both cytokines induced expression of cell-surface IL-2R alpha (CD25) on freshly isolated human peripheral blood mononuclear cells (PBMC) in the absence of other exogenous stimuli. They also stimulated the release of soluble IL-2R alpha and induced proliferation of these cells in 1-week cultures in a time- and dose-dependent manner. Recombinant IL-7 could also induce the expression of CD25, although sIL-2R alpha was released at only low levels. In monocyte-depleted PBMC the sIL-2R alpha release was minimal. When isolated T cells or non-T cells were stimulated by rIL-15 or rIL-2, cell surface CD25 was expressed, but released sIL-2R alpha was undetectable. On stimulation with rIL-15, more than 80% of all natural killer cells expressed CD25 and more CD8br+ lymphocytes were positive for CD25 compared to stimulation by rIL-2. These results may be clinically relevant because several diseases are associated with high serum levels of sIL-2R alpha which may he not only due to IL-2 but also due to IL-15 stimulation.

Studies of the expression of the Wiskott-Aldrich syndrome protein.

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by thrombocytopenia, eczema, disorders in cell-mediated and humoral immunity, and a proclivity to lymphoproliferative disease. The gene responsible encodes a 53-kD proline-rich protein of unknown function (WASP). We produced a FLAG-WASP fusion protein that was used to immunize mice and produce mAbs against WASP. Using monoclonal anti-WASP in Western immunoblots, we have determined that WASP is present in the cytoplasmic but not nuclear fraction of normal human peripheral blood mononuclear cells, in normal human platelets, in T lymphocytes, non-T lymphocytes, and monocytes. The protein is produced in the B cell immunoblastic cell line DS-1, in normal EBV-transformed B cell lines, and in HEL92.1.7, but is barely detectable in MOLT-4 and not detectable in K562. WASP was present in two of four EBV-transformed cell lines from WAS patients. Splenic tissue immunostaining was performed in two patients, and the results correlated with the results of the Western blots. Sequence analysis of WASP cDNA from two patients who produce WASP show mutations causing amino acid substitutions. These studies establish a foundation for further studies aimed at understanding the function of WASP.

IL-15 induces the release of soluble IL-2Ralpha from human peripheral blood mononuclear cells.

The recently identified and cloned cytokine IL-15 shares many of the T-cell and B-cell stimulatory activities of IL-2 and utilizes the beta and gamma chains of the IL-2R for binding and signaling. The present report shows that, like IL-2, IL-15 in a concentration and time-dependent manner causes the release of sIL-2Ralpha from PHA-activated human peripheral blood mononuclear cells. This effect of IL-15 is largely direct and independent of IL-2. Blocking of the IL-2Rbeta chain with the antibody Mik-beta1 prevented the release of sIL-2Ralpha by IL-15 but not by IL-2. IL-7, another cytokine utilizing the gamma chain of the IL-2R, drove the release of sIL-2Ralpha as well. Several clinical conditions are associated with abnormal serum sIL-2Ralpha levels and are also monitored by the measurement of sIL-2Ralpha. The reason for sIL-2Ralpha release is not fully understood. In this study, IL-15, like IL-2 was shown to be a potent inducer of sIL-2Ralpha release in vitro.

Soluble interleukin-2 receptor alpha is elevated in sera of patients with benign ovarian neoplasms and epithelial ovarian cancer.

BACKGROUND: Previous studies have established that soluble interleukin-2 receptor alpha (sIL-2R alpha) levels are elevated in ascites and sera from individuals with advanced ovarian cancer (International Federation of Gynecology and Obstetrics [FIGO] Stage III/IV). This study was undertaken to evaluate sIL-2R alpha levels in individuals with benign ovarian neoplasms and early stage ovarian cancer (FIGO Stage I/II). Comparison with CA 125 levels was performed to assess screening potential. METHODS: Sera from 92 healthy individuals, 61 with benign adnexal masses, 12 patients with FIGO Stage I/II ovarian cancers, and 27 patients with FIGO Stage III/IV ovarian cancers were assayed for sIL-2R alpha by enzyme-linked immunosorbent assay and CA 125 by radioimmunoassay. RESULTS: The mean serum sIL-2R alpha levels for benign pelvic masses, and Stage I/II and Stage III/IV epithelial ovarian cancer were 1507 +/- 82, 1631 +/- 274, and 2596 +/- 384 U/ml, respectively. The difference between mean serum sIL-2R alpha levels in individuals with benign adnexal masses and Stage III/IV epithelial ovarian cancer was statistically significant (P < 0.05). In addition, of the four individuals with FIGO Stage I/II ovarian cancer who had CA125 levels below 35 U/ml, the accepted upper limit of normal, three patients had elevated serum sIL-2R alpha levels. Eleven of 12 patients (92%) with potentially curable Stage I/II disease had elevated serum levels of either sIL-2R alpha or CA125 and 8 of 12 (67%) had elevations of both sIL-2R alpha and CA125. Sensitivity and specificity of a combination of CA 125 and soluble IL-2R alpha were 88.5% and 27.1%, respectively. CONCLUSION: Soluble interleukin-2 receptor alpha levels do not appear to differentiate between benign adnexal lesions and early malignancy; however, measurement of sIL-2R alpha levels in combination with CA125 warrants further evaluation to determine if together they will identify individuals with Stages I and II ovarian cancer.

Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency.

In 1980 the clinical syndrome of X-linked hypogammaglobulinemia and isolated growth hormone deficiency (XLA/GHD) was described. XLA/GHD patients have reduced serum levels of Ig and normal cell-mediated immunity, and thus resemble patients with Bruton's X-linked agammaglobulinemia (XLA). However, XLA/GHD patients also have isolated GHD. Mutations and deletions in the Bruton's tyrosine kinase gene (BTK) are responsible for Bruton's XLA. We investigated BTK gene expression in an XLA/GHD patient from the family originally described by Northern analysis, cDNA sequencing, and Western analysis of protein production using mAb to BTK. BTK mRNA was normal in size and abundance, and the mRNA sequence was normal over the coding region, except for a single silent mutation. BTK protein was present in normal amounts in PBMC of this patient. Thus, at the molecular level, XLA/GHD is a different disease entity from Bruton's XLA. These results suggest that undescribed genes critical for B cell development and growth hormone production exist on the X chromosome.

Production of monoclonal antibodies to Bruton's tyrosine kinase.

Bruton's X-linked agammaglobulinemia is caused by mutations in a cytoplasmic protein tyrosine kinase termed Bruton's tyrosine kinase (BTK). The protein is expressed in all members of the B cell lineage and is critical for B cell development. The protein consists of several modules, including a pleckstrin homology domain and the Src homology domains SH1, SH2, and SH3. We report here the production of monoclonal antibodies against the pleckstrin homology domain of human BTK. The antibody was produced by immunizing mice with a FLAG-BTK fusion protein. Hybridoma supernatants were screened by ELISA using a GST-BTK fusion protein as the antigen. Selected monoclonal antibodies recognize denatured BTK on Western blots of peripheral blood mononuclear cell lysates. Mouse BTK protein is also detected. These antibodies should be useful in assessing patients with immune deficiency, as well as in studying normal B cell development.

Racial differences in serum immunoglobulin levels: relationship to cigarette smoking, T-cell subsets, and soluble interleukin-2 receptors.

To investigate the influence of race, cigarette smoking, and immunologic parameters on serum immunoglobulins, we analyzed serum IgG, IgA, and IgM levels in 455 healthy adults. The study population ranged in age from 20 to 69 years, including 282 whites and 173 blacks, 181 never-smokers, 93 ex-smokers, and 181 current smokers. Race and smoking were independently associated with alterations in serum IgG levels. Blacks had significantly higher IgG levels than whites (1,587 vs. 1,209 mg/dl; P < 0.001), and never smokers had significantly higher levels than current smokers (1,426 vs. 1,287 vs. mg/dl; P < 0.001). IgA and IgM levels were unrelated to race or smoking. Serum IgG was also found to be directly related to the proportion of HLA-DR+ cells and the level of soluble interleukin-2 receptors (sIL-2R) and inversely related to the proportion of CD4+ cells. Investigation of this racial heterogeneity may provide insights into the pathogenesis of immunologic diseases that exhibit unexplained racial variation.

Factors influencing serum neopterin and beta 2-microglobulin levels in a healthy diverse population.

Sera and questionnaire data from a population-based random sample of healthy adults was used to evaluate factors influencing neopterin and beta 2-microglobulin (beta 2m) values. Both neopterin and beta 2m levels increased with age and were higher among white than blacks (mean values for whites and blacks: neopterin, 5.06 vs 4.49 nmol/L; beta 2m, 1.36 vs 1.28 mg/L). Gender differences were noted for beta 2m but not neopterin values (beta 2m males vs females: 1.37 vs 1.29 mg/L). Neopterin values were lower among current smokers than among nonsmokers (4.32 vs 5.16 nmol/L) and were higher among users of antihistamines (5.46 among users vs 4.65 nmol/L among nonusers). Neopterin and beta 2m were correlated in this healthy adult population (adjusted r = 0.53, P = 0.001), yet no other interrelationships with numerous biologic markers except between beta 2m and serum-soluble interleukin-2 receptor levels (adjusted r = .41, P = 0.05) were observed. These findings provide important baseline information to consider before planning or evaluating studies utilizing neopterin or beta 2m levels.

Molecular genetic analysis of the primary immunodeficiency disorders.

Exciting progress in the search for the genetic basis of the primary immune deficiency disorders continues to shed insight into functioning of the immune system in health and disease. The molecular genetic causes of 7 of the 17 WHO-recognized primary immune deficiency diseases have been defined. Additional studies will shed more insight into congenital and acquired immune deficiency disorders.

Targeting human IL-2 receptors for diagnosis and therapy.

The high-affinity interleukin-2 receptor (IL-2R) is a multichain receptor with at least three IL-2 binding chains: IL-2R alpha (55 kDa) bound by the monoclonal antibody anti-Tac, IL-2R beta (75 kDa) and Il-2R gamma (64 kDa). The IL-2R alpha also exists as a naturally occurring soluble molecule (sIL-2R alpha). We target the IL-2R for immune intervention since resting normal cells do not express the high-affinity IL-2R, whereas this receptor is on some cells in certain lymphoid neoplasias, select autoimmune disorders, and in individuals rejecting organ allografts. Treatments have included unmodified murine anti-Tac and radioisotopes conjugated to murine anti-Tac. Our emerging understanding of the IL-2R system continues to open possibilities for more specific immune intervention.

Racial variation in serum-soluble interleukin-2 receptor levels: a population-based study of healthy smokers and nonsmokers.

To investigate the influence of race and cigarette smoking on serum levels of soluble interleukin-2 receptors (sIL-2R), we studied a population-based cohort of 282 white and 173 black adults, ages 20-69 years. Serum sIL-2R concentrations in this healthy population ranged from 146 to 2623 U/ml. Whites had significantly higher sIL-2R levels than blacks (455 versus 365 U/ml; P < 0.001), and cigarette smokers had significantly higher levels than nonsmokers (508 versus 420 U/ml; P = 0.01). White smokers had the highest levels (550 U/ml); white nonsmokers and black smokers had intermediate levels (455 and 450 U/ml, respectively); and black nonsmokers had the lowest levels (365 U/ml). Smoking cessation appeared to normalize sIL-2R levels; exsmokers who had not smoked for at least 2 years had sIL-2R levels similar to those of never smokers. These data demonstrate the wide range of serum sIL-2R concentrations found in normal healthy adults and the significant influence of race and cigarette smoking. Further investigation of this natural heterogeneity may provide insights into the mechanisms underlying genetic and environmental influences on this important immunologic parameter.

Characterization of a new IL-6-dependent human B-lymphoma cell line in long term culture.

We have established a cell line (DS-1) of B-cell lineage in long-term culture. It was derived from an immunodeficient patient with intestinal lymphangiectasia and lymphoma by culturing malignant pleural effusion cells with IL-6 in vitro. The cell surface phenotype was; PCA-1, HLA Class II(+); CD25, CD19, CD20, CD30, CD38(-). Cell proliferation was poor in medium and exhibited an eight-fold, dose-dependent increase of proliferation in response to rIL-6 of human but not murine origin. The secretion of IgG into culture supernatants by DS-1 was not enhanced by rIL-6. While constitutive production of IL-6 was not detected by bioassay using murine B9 hybridoma cells or by ELISA, the presence of IL-6 message was detected in polyA+ selected mRNA by Northern analysis. Spontaneous proliferation of DS-1 cells was inhibited by neutralizing polyclonal antibodies to IL-6 (37%) and mAb to IL-6 (54%) and IL-6R (53%). DS-1 expressed both high and low affinity IL-6 receptors (Kd 1.2 x 10(-11) and 6.7 x 10(-10), respectively) by radiolabelled binding and Scatchard analysis. Thus, DS-1 represents an autocrine IL-6-producing cell line of B-cell lineage which resembles lymphoid malignancies arising in patients with AIDS and other immunodeficiency diseases. Despite constitutive IL-6 production, the in vitro growth of DS-1 is dependent upon exogenous IL-6. DS-1 may thus be useful as a model of IL-6 dependency. This cell line may also facilitate development of strategies for diagnosis and treatment of B-cell lymphomas in immunocompromised patients.

Serial levels of soluble interleukin 2 receptor in the peripheral blood of patients with rheumatoid arthritis: correlations with disease activity.

We serially assayed soluble interleukin 2 receptor (sIL-2R) levels in the peripheral blood (PB) of 22 patients with rheumatoid arthritis (RA) followed for a period of 12 months, and correlated these levels with disease activity. We examined the relationship between the direction in which each of the disease measures changed between assessments and the direction of change in sequential sIL-2R levels. In 22 of the 25 (88%) instances where there was a 30% change in the active joint count between sequential assessments, the direction of change of the PB sIL-2R level was found to be in parallel (chi 2 = 11.7, p less than 0.008). Our results suggest that serial sIL-2R levels are a useful means of confirming clinically significant changes in disease activity in patients with RA, irrespective of therapy.

Elevated serum levels of soluble Tac peptide in adult T-cell leukemia: correlation with clinical status during chemotherapy.

Adult T-cell leukemia associated with human T-cell leukemia virus type I (HTLV-I) is characterized by a clonal expansion of a CD4-positive subset of T lymphocytes that constitutively express high numbers of interleukin-2 receptors and that frequently infiltrate the skin; osteolytic bone lesions, and hypercalcemia. Using an enzyme-linked immunosorbent assay (ELISA) test, we measured the level of soluble Tac peptide, one chain of the human interleukin-2 receptor, in the serum of 50 patients with adult T-cell leukemia (38 Japanese and 12 American patients), 8 patients with other hematologic malignancies, 8 asymptomatic HTLV-I-antibody-positive carriers, and 17 normal controls. The serum level of soluble Tac peptide (geometric mean U/mL, 95% CI) was elevated at presentation in all patients with adult T-cell leukemia (16,461; 819 to 330,896) when compared with normal controls (238; 112 to 502), patients with other hematologic malignancies (1302; 475 to 3569), and healthy HTLV-I antibody-positive carriers (490; 115 to 2086). The highest levels were seen in patients (n = 33) with acute (32,154; 2587 to 399,598) compared with chronic (5464; 661 to 45,156) disease (n = 14). Serum levels of Tac peptide also tended to be more elevated in patients with adult T-cell leukemia with hypercalcemia (32,072; 2461 to 417,908) compared with normocalcemic patients (13,885; 496 to 388,436). Serial measurements of soluble Tac peptide levels in serum were done in four patients with adult T-cell leukemia during chemotherapy and the levels reflected disease activity. These observations suggest that the measurement of soluble Tac peptide levels in patients with adult T-cell leukemia is useful as a noninvasive measure of tumor burden and will help in the diagnosis of the disease and management of these patients.