Krco, Christopher J.

Abstract Mice bearing the autosomal recessive gene "wasted" (wst/wst) have been reported to develop low or absent secretory immune responses, abnormal DNA repair mechanisms, and uncoordinated body movements. We have performed a detailed immunologic and neuropathologic investigation of the disease. Con A and LPS mitogenic responses of splenic lymphocytes as well as total serum Ig levels were equivalent in wst/wst and undiseased control littermates (wst/+ and +/+). Amounts of serum IgM, IgG2a, IgG2b, IgG3, and IgA, however, were reduced in wst/wst animals. FACS analyses of Ig+ and isotype-specific B cell populations revealed similar percentages of Ig+, mu +, gamma +, and alpha + cells in wst/wst and control mice. However, the percentage of "very bright" Ig+ cells as well as "very bright" heavy and light chain-specific B cell subpopulations was increased at least 10-fold in wst/wst B cells as compared with littermate controls. In addition, studies of Ig-specific mRNA accumulation in these animals revealed significant decreases in all isotypes except gamma 3 in spleens of wst/wst mice as compared with littermate controls. Neuropathologic studies in wst/wst mice showed prominent vacuolar degeneration of neurons within anterior horns of the spinal cord and the motor nuclei of the brain stem. No abnormalities were noted in Purkinje cells of the cerebellum nor within myelin sheaths. The abnormalities in the nervous system resembled human motor neuron disease rather than ataxia-telangiectasia as had been reported previously. The immunologic studies suggest that splenic B cells from wst/wst mice have a defect in the ability to "switch" from membrane to secreted Ig. In addition, this mutation provides a mechanism to study regulatory interactions between the immune and nervous systems.

Abstract A series of seven I-Ab-reactive monoclonal antibodies (mAb) has been derived from a BALB/c anti-C57BL/6 immunization. Analysis of the reactivity patterns of these mAb with spleen cells of mice from the independent haplotypes has revealed three groups of mAb: group I mAb react with all haplotypes except d, group II with all except d and k, and group III with all except d, k, and j. In addition, the group I and group II mAb also react with human class II-expressing cells. We have used these mAb to isolate one mutant I-Ab-expressing cell line and three additional I-Ak mutant cell lines. These antibodies have been used, in conjunction with a large panel of I-A-reactive mAb available from others, to extensively characterize our collection of mutant I-A-expressing cell lines. Analysis of the mutant cell lines has allowed us to assign the reactivity of each mAb to either the A alpha- or the A beta-polypeptide. All seven newly isolated mAb appear to react with determinants on the A alpha-polypeptide. Furthermore, analysis of the panel of A alpha k- and A beta k-mutants has allowed us to discriminate at least five epitopes that are separable by mutation on the A beta k-polypeptide, and two epitopes on the A alpha k-polypeptide.

Abstract Immunoblot analysis was used to characterize the Trichinella spiralis L1 larval Ag recognized by antisera from T. spiralis-infected AKR/J mice. Antisera were analyzed for reactivity with crude worm extract, excretory/secretory proteins and cuticle proteins from L1 larvae. The response was biphasic; antibodies against one set of Ag were detected 13 days after infection (group I Ag), and antibodies against a different set of Ag were detected 35 days after infection (group II Ag). Excretory/secretory and cuticle proteins were recognized only by antibodies produced late in infection. The predominant isotype in day 42 antiserum was IgG1, and 80% of these IgG1 antibodies reacted with a stage-specific determinant shared by virtually all group II Ag. A mAb reactive with the shared determinant was used to purify the group II Ag from L1 larval extract. Such affinity-purified Ag were protective when used to immunize mice against subsequent infection, and T cells from infected mice proliferated when cultured with these Ag in vitro. Other mouse strains also made a strong serum antibody response to the group II Ag. We hypothesize that immune responses to the shared epitope play an important role in determining the outcome of the host-parasite interaction during infection.

Abstract When MHC congenic and recombinant mice are inoculated with Torpedo acetylcholine receptors (AChR) with adjuvants, the magnitude of autoantibody responses to muscle AChR and the defect of neuromuscular transmission closely parallel in vitro lymphocyte proliferative responses to Torpedo AChR. All of these responses are controlled by gene(s) at the I-A subregion of the H-2 complex. Data presented in this report confirm in back-cross mice that T lymphocyte proliferative responses to AChR are controlled by a Mendelian dominant gene linked to H-2, at the I-A subregion. Lymphocyte responses were eliminated by blocking Ia antigens on lymph node cell surfaces with appropriate anti-I-A alloantisera and by removal of adherent cells. A spontaneous mutation at the I-A subregion in the B6 strain, which resulted in structural alteration of the A beta chain of Ia, converted high responsiveness to AChR to a state of low responsiveness. These data implicate a macrophage-associated Ia molecule in induction of autoimmune responses to AchR, probably in the presentation of AChR to helper T lymphocytes that thereby help B lymphocytes to differentiate into anti-AChR antibody-forming cells.

Abstract The proliferative response of regional lymph node lymphocytes to Torpedo acetylcholine receptor (TAR) is under H-2 linked Ir gene control. In high responder B6 (H-2b) congenic mice, lymphocytes that proliferate in vitro in response to TAR are dependent on T cells of a subpopulation expressing the phenotype associated with helper functions, Lyt-1+23-.

3037 Background: Tumor immunotherapies directed towards enhancing natural or endogenous anti-tumor T-cell immunity in patients with advanced malignancies are currently being implemented in clinic with promising results. In order to optimize therapeutic protocols and monitor the effectiveness of such therapies, a reliable T-cell marker is needed. Methods: We utilized CD11a (LFA-1, lymphocyte functional-associated antigen 1), an integrin up-regulated on effector and memory CD8 T-cells, and PD-1 (programmed death-1), an immunoregulatory receptor expressed by activated T cells, as biomarkers to identify, quantitate and monitor endogenous tumor-reactive cytotoxic lymphocytes (CTLs) in two mouse tumor models and the peripheral blood (PB) of 12 patients with stage IV melanoma. Results: High expression of CD11a and PD-1 was identified among CD8 T-cells residing within primary and metastatic murine tumor sites, as well as in spontaneous murine breast cancer tissues. In the PB of melanoma patients, tumor antigen-specific CD8 T cells were associated with a population of CD11a high CD8 T-cells which co-expressed high levels of PD-1, as opposed to eleven healthy donors who had a much lower frequency of PD-1+ CD11a high CD8 T-cells (p <0.0001). Phenotypic analysis showed that CD11a high CD8 T-cells are proliferating (Ki67 positive) activated (CD62L low, CD69 high) T-cells. Increased CD11a high CD8 T-cells and delayed tumor growth were observed in PD-1 deficient mice, suggesting that the antitumor effector function of CD8 T cells is compromised by co-expression of elevated levels of PD-1. Conclusions: CD11a high CD8 T-cell population expresses high levels of PD-1 and is likely the cellular target of PD-1 blockade therapy. High expression of CD11a (LFA-1) and PD-1 (CD279) by CD8 T-cells may represent a novel biomarker to identify and monitor endogenous tumor-reactive CTLs. This may not only provide an immunological readout for evaluating the efficacy of therapy, but also contribute to the selection of patients with solid malignancies likely to benefit from anti-PD-1 therapy.

20043 Background: Studies have demonstrated that the generation of endogenous immunity to specific tumor antigens is associated with improved prognosis for many cancers. Thus, there has been increased efforts to identify tumor-associated antigens to which there is immunity, as these may be tumor rejection antigens. A candidate antigen is the folate receptor alpha (FRα) which is overexpressed in malignancies, especially breast and ovarian cancer. Prior studies involving ovarian and breast cancer patients have demonstrated the presence of FRα-specific cytotoxic T cells in the tumor-associated lymphocyte population. Methods: Using the RANKPEP CD4 T cell epitope prediction algorithm, we predicted promiscuous immunogenic regions of FRα, and tested for immunity in 30 breast or ovarian cancer patients and 18 healthy volunteer donors in order to attain a better understanding of the levels and extent of the endogenous FRα immune response. Immunity was examined using IFN-γ ELIspot analysis and IgG ELISAs. Results: Fourteen peptides were predicted as potential epitopes to which T cells may respond, seven each from the carboxy- and amino-terminus halves of the protein. Greater than 70% of patients demonstrated T cell immunity to at least one of the fourteen peptides. Patients responded to an average of 3 ± 0.7 peptides while healthy donors responded to only 1 ± 0.5 peptides (p = 0.02). Five peptides were recognized by >25% of patients. Responses to three of these peptides were higher (p > 0.05) in the patients than in healthy donors, suggesting that patients generated immunity upon cancer development. Compared to healthy individuals, patients developed higher immunity to the amino-terminus half of the receptor, suggesting natural epitope spreading (p = 0.03). There was no difference between patients and healthy donors in the immune responses to either non-specific stimuli (p = 0.2) or viral peptides (p = 0.5). Patients had detectable FRα-specific IgG antibody consistent with active FRα-specific helper T cell immunity. Conclusions: These findings demonstrate that the FRα is a target of the immune system in patients with breast or ovarian cancer. Understanding the antigens that are naturally targeted by the immune system may be important for diagnosis, prognosis, and immune-based therapies. No significant financial relationships to disclose.

Abstract In this sequential assay, the thyroglobulin in serum binds to polystyrene beads coated with two mouse monoclonal antibodies. These beads then react with a rabbit polyclonal antibody, biotinylated sheep anti-rabbit IgG, streptavidin-horseradish peroxidase, and a peroxidase substrate to yield a colored product that is measured spectrophotometrically at 492 nm. The range of the standard curve is 1.6 to 100 micrograms/L. The detection limit of the assay is 1.2 micrograms/L. The interassay coefficient of variation is 14.0% at 6.2 micrograms/L, 5.7% at 32.7 micrograms/L; the intra-assay CVs range from 7.8% to 14.8%. The reference intervals are 2.7 to 42.1 micrograms/L for euthyroid persons and less than or equal to 5 micrograms/L for athyreotic patients not on thyroxin replacement therapy. Some autoantibodies to thyroglobulin cause thyroglobulin values to be falsely low. The concentration of autoantibodies is not correlated with the analytical recovery of human thyroglobulin. The coefficient of correlation between the measurement of thyroglobulin by this assay and by an immunoradiometric assay was 0.969 for 186 autoantibody-negative samples, 0.963 for 37 autoantibody-positive samples.