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Immunologically Mediated Diseases and Allergic Reactions
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Kim A. Campbell, Caroline C. Whitacre
The central role of the immune system is to discriminate self from nonself. Competent lymphocytes must recognize and respond to foreign antigens, yet remain nonresponsive to self-antigens. In order to avoid autoreactivity, the immune system functions within the confines of self-tolerance, which is defined simply as the unresponsiveness of the immune system to a self-antigen. Tolerance mechanisms actively prevent the maturation and expansion of potentially self-reactive lymphocytes to maintain a self-tolerant repertoire of mature immune cells, as discussed in chapter 8. Self-tolerance mechanisms include (1) the deletion of all self-reactive lymphocytes during their maturation, (2) the preferential inactivation of helper T cells specific for self-antigens, and (3) the suppression of self-reactive T cells by regulatory cells. How then is it possible that autoimmune responses are generated in light of the fact that control mechanisms are working to prevent such occurrences? Autoimmune responses result from a breakdown of immunological tolerance. There may be an abnormal selection of self-reactive lymphocytes or an inappropriate stimulation of normally nonresponsive or anergic T cells. A breakdown in tolerance may also occur as a result of inhibiting suppressive surveillance mechanisms, or there may be a release of antigens that are normally inaccessible to immune recognition. A number of factors may be responsible for breaking self-tolerance, including genetic predispositions, infections, or immunological anomalies.
Gene Rearrangement in Leukemias and Lymphomas
Published in John T. Kemshead, Pediatric Tumors: Immunological and Molecular Markers, 2020
The analysis of Ig gene configurations in lymphomas was a natural extension of the studies on leukemia. The Southern blot technique facilitates the identification of a minority population of clonal B cells within a variety of normal cell types.41 This is of particular value in cases where reactive lymphocytes, which are difficult to distinguish from neoplastic lymphoid cells, are present or when the conventional pathological data are insufficient to differentiate between lymphoma and other conditions, e.g., an undifferentiated carcinoma.
Allogeneic Hematopoietic Stem Cell Transplantation for Autoimmune Diseases
Published in Richard K. Burt, Alberto M. Marmont, Stem Cell Therapy for Autoimmune Disease, 2019
Shimon Slavin, Alberto Marmont, Richard K. Burt
Autoimmune diseases result from self-reactive T-lymphocytes and autoantibodies, produced most likely in cooperation with T-cell dependent B-cells. Until recently, non-specific suppression of self-reactive lymphocytes or the inflammatory process mediated by the ongoing anti-self reactivity represented the main goal of therapy, but in the large majority of cases, neither cure nor remission can be obtained. Patients with severe, life threatening, manifestations of autoimmune diseases such as multiple sclerosis (MS), systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) may require long-term maintenance immunosuppressive treatment similar to organ allograft recipients, with all the anticipated side effects related to chronic immunosuppression on the one hand and side effects directly related to the immunosuppressive drugs (e.g., corticosteroids, cytotoxic agents and cyclosporin A to mention just a few) on the other. Unfortunately, none of the approaches available to date can offer effective and safe regulation of anti-self reactivity. Clearly, reinduction of unresponsiveness to-wards self antigens remains the yet unaccomplished final goal.
Extranodal natural killer/T-cell lymphoma nasal type
Published in Baylor University Medical Center Proceedings, 2022
Benjamin S. Daines, Rahul M. Varman, Tam Q. Nguyen
The patient returned months later with worsening symptoms and agreed to bilateral submucosal resection of the inferior turbinates with sphenopalatine cryosurgical ablation. Mucosal biopsies demonstrated reactive lymphocytes. Symptoms improved initially, but she worsened 3 months postoperatively and presented with facial swelling, fever, and nasal obstruction. The white blood cell count was within normal limits. CT of the head demonstrated pansinusitis (Figure 1b) necessitating bilateral maxillary functional endoscopic sinus surgery (FESS) with debridement of necrotic tissue. Biopsies were negative for Mucor species and lymphoma. A repeat FESS with bilateral maxillary antrostomy, ethmoidotomy, and sphenoidotomy was performed for recurrent symptoms with discharge 1 week postoperatively.
Platelet parameters and leukocyte morphology is altered in COVID-19 patients compared to non-COVID-19 patients with similar symptomatology
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2021
Anne Alnor, Maria Boysen Sandberg, Barbara Ella Toftanes, Pernille Just Vinholt
We furthermore found lower levels of reactive lymphocytes to be associated with COVID-19. Reactive lymphocytes are frequent in viral infections, and increased frequencies of reactive lymphocytes have been described in case studies of COVID-19 patients [3,14]. The discrepancy between the case studies and our findings may be because we carried out smear examination regardless of sample flagging by the automated haematology equipment to make sure that the morphological population did not only include abnormal samples, as this could lead to overestimations. Differences in population size may furthermore contribute to discrepancies. In the present study, lymphopenia was more pronounced in COVID-19 with severe disease courses, but the percentage of reactive lymphocytes was not. Lymphopenia has been consistently reported to be associated with severe COVID-19 [2]. Also, lymphocytes and functional exhaustion of cytotoxic lymphocytes have been found to be directly involved in COVID-19 disease progression [15,16].
How I approach new onset thrombocytopenia
Published in Platelets, 2020
Blood film examination is pivotal and careful attention should be directed to all cell lines. Recognition of schistocytes is critical for assessment and exclusion of MAHAs, such as TTP. Red cells should be examined for spherocytes and polychromasia, which would point to associated hemolysis (Evans syndrome). White cells should be examined for the presence of immature forms, which would suggest a hematological malignancy; or reactive lymphocytes, as seen in acute viral infections such as dengue or cytomegalovirus infection. Platelets should be inspected for number, size, and granularity. Platelet size, either estimated from blood film review or measured by the analyzer (reported as mean platelet volume (MPV)) can be useful to guide molecular analysis in suspected hereditary thrombocytopenia syndromes as these can be categorized according to expected platelet size (Table II).