Plasma Cell Reaction Research Articles

Features of Cell Reactions during Implantation of Biodegradable Polymer and Polypropylene in the Experiment.

Quantitative and qualitative characteristics of cell infiltrates in male Wistar rats were studied from 14 days to 12 months after implantation of polypropylene and a biodegradable polymer obtained by electrospinning and consisting of 65% polycaprolactone and 35% polytrimethylene carbonate. It was found that a predominantly macrophage-giant cell reaction developed around the biodegradable polymer; it spread into the matrix and the number of cells in the infiltrate decreased, as the degradation progressed. Around polypropylene, mainly lymphocytic and leukocytic reaction was seen; it also decreased with time, but was characterized by a reverse increase in the number of lymphocytes. Immunohistochemical analysis showed that the proportion of CD38+ cells 12 months after implantation increased around polypropylene to a greater extent than around the biodegradable polymer, while the proportion of CD68+ cells decreased. These findings suggest that implantation of a biodegradable polymer caused no prolonged lymphocytic and plasma cell reaction in animals as in the case of polypropylene, which indicates that biodegradable polymer is a promising material for tissue engineering.

P064 Association Between Crohn's Disease (CD) and Transient IgM and IgG Immunodeficiency-Diagnostic and Management Challenges.

Background: CD is an inflammatory disease that predominantly affects the gastrointestinal tract and has a progressive course. Immunodeficiencies can occur by altering different components of innate or adaptive immune responses. Such changes put the patient at greater risk for infectious diseases or non-infectious complications. Among the non-infectious complications are cancer, autoimmune diseases and gastrointestinal diseases, which should be suspected in patients with recurrent infections, with clinical, radiological or histological features of the disease are atypical or in the occurrence of an unsatisfactory response to conventional therapy. To describe a case report of a CD patient complicated with enteric alterations related to immunodeficiency. A 31-year-old male patient started presenting abdominal pain, diarrhea, and weight loss in October 2020. He underwent a colonoscopy that showed diffuse involvement of the colon suggestive of CD. He didn`t respond to therapy with prednisone and azathioprine and lost 40kg until January 2021, when he was referred to an IBD center. He had signs of malnutrition (eg, BMI = 15.4, Albumin = 1.8g/dL). The MRI showed diffuse thickening of the walls of the entire length of the ileum, colon and rectum, associated with submucosal edema and more intense enhancement in the inner layer. Findings compatible with nonspecific diffuse ileocolitis. After negative infectious screening, hydrocortisone, azathioprine and infliximab were prescribed, but the patient remained clinical worsening. During the 6 weeks of therapy use, the patient presented oral candidiasis, septic pyoarthritis, DNA testing for Clostridium difficile and PCR for Cytomegalovius were positive. Despite the treatment of infectious diseases, the patient continued to worsen and was considered a primary non-response to anti-TNF, opting for the initiation of Ustekinumab. There was improvement in endoscopic and fecal calprotectin, but continued progression of ileal disease and diarrhea, with no response to enteral or parenteral nutritional therapies. An investigation for immunodeficiencies was carried out and IgM/IgG deficiency was noted, and parenteral immunoglobulin was started. He presented an intestinal subocclusion, requiring a loop ileostomy. In this surgery, it was decided to send a sample of ileal tissue for diagnostic differentiation, where ileitis was observed with intense plasma cell reaction and lymphoid nodular hyperplasia, uncharacteristic of DC, which may correspond to enteropathy secondary to immunodeficiency. Despite the treatment, the patient presented fungal endocarditis, esophageal moniliasis and septic condition of undetermined origin. He remained in hospital for 120 days until complete improvement of the infectious complications. With the slow improvement in nutritional parameters, there was a reduction in the incidence of infections as well as an increase in immunoglobulins. After five months of combined nutrition and anti-interleukin therapy, the patient presented clinical improvement, weight gain and complete normalization of IgG and IgM. Ileal disease is in regression and in the colon, in endoscopic remission. We present a case report of the initial presentation of DC complicated with severe malnutrition where there was depletion of part of immunoglobulins, resulting in infectious and non-infectious complications, where ileal involvement intensified the manifestation of colonic DC.

Morphology of the chicken sleep and its changes during vaccination

A significant number of scientific work has been dedicated to the study of immunogenesis processes in birds vaccinated to infectious diseases. In most contingency, research is aimed at assessing postvaccination immunity, as well as establishing structural changes in the immune system. But, exactly morphological studies that can provide an objective account of the immune effectiveness of the vaccine and assess the state of the body's immune system. However, today, morphological control of the immune status of chickens in the post-vaccination period has not been multitudinous used in practical poultry farming. Creating new vaccine prevention schemes, experts do not take into account the changes that manifested during this period. The purpose of the article – Is to systematize and describe the main results of research on the morphology of the spleen of chickens during vaccination. It should be noted that infectious diseases of birds, occupied a special place are: infectious bursal disease, infectious bronchitis, Newcastle disease, infectious laryngotracheitis, etc. Now, these diseases are registered in almost all countries of the world and bring significant economic losses to poultry farms. The main morphological changes in the spleen of chickens during vaccination include hyperplastic processes (lymphocyte proliferation and enlargement of macrophages), the appearance of blast cells, the development of plasma cell reactions. Morphofunctional changes in the spleen of chickens during vaccination are reflected in a significant amount of literature, but changes in the body that occur with multiplex vaccinations during complex vaccination schemes are not enough covered. This review article put a short description of the effect of vaccination used worldwide on the morphology of the spleen of chickens. The received data of a complex assessment of the morphofunctional state of the bird's spleen at different ages should be taken into account when compare complex scheme of vaccination.

First psychotic episode as first manifestation of lyme disease: Case report

IntroductionLyme disease (LD) is caused by the spirochete Borrelia burgdorferi (Bb) and has been reported to be associated with various psychiatric presentations.ObjectivesTo report a case with LD and to highlight the importance of differential diagnosis in a first psychotic episode.MethodsCase report and non-systematic review of the literature.Results A woman aged 31 was admitted to the psychiatric department, after a car accident with a mortal victim, due to a first psychotic episode with visual hallucinations, disorientation in time and space, persecutory and grandiosity delusions. She had a personal psychiatric history of obsessive-compulsive disorder and no previous admission to an inpatient Unit. On psychotropic drugs the condition failed to improve, and subsequently neurological symptoms developed. EEG abnormalities prompted a lumbar puncture. In the CSF a strong plasma cell reaction with atypical cells was observed. The enzyme immunoassay for Borrelia burgdorferi was positive and after treatment with penicillin the psychiatric and neurological signs and symptoms remitted. Screening assessment followed by a thorough history, comprehensive psychiatric clinical exam, review of systems, mental status exam, neurological exam and physical exam relevant to the patient’s complaints and findings with clinical judgment, pattern recognition and knowledgeable interpretation of laboratory findings facilitates diagnosis. Psychotropics and antibiotics may help improve functioning and prevent further disease progression.ConclusionsLD is relatively rare, but awareness of the association between LD and neuropsychiatric presentations can improve understanding of the causes of mental illness and result in more effective prevention, diagnosis and treatment.DisclosureNo significant relationships.

Clinical and morphological manifestation of spontaneous Coxiella burnetii infection in sheep

The study that simultaneously employed negative staining and ultra-thin sectioning to investigate the causative agent of Q fever in phase I showed that the epizootic strain exhibited morphological characters typical of C. burnetii. Investigation of the ultra-thin structure of sections and whole racketetia cells of the epizootic strain revealed clearly expressed structural basis of the elements of their arrangement and partial similarity of the strain to the reference strains. In animals infected with spontaneous Q fever, the clinical course of the disease was characterized as severe with signs of intermittent fever up to 42 °C, symptoms of fatigue, decreased food excitability, inactivity, catarrhal rhinitis and conjunctivitis, and cyanosis of mucous membranes. Specific, nonspecific and immunopathological processes developed in organs and tissues: specific changes were characterized by formation of epithelioid cell granulomas with Pirogov-Langhans giant cells in the lymph nodes; nonspecific changes manifested through hyperplastic, macrophage and plasma-cell reactions in lymphoid organs; immunopathological changes were characterized by indurated and fibrotized reticular stroma of lymphoid organs, plasmorrhagia, erythrodiapedesis, mucoid and fibrinoid swelling of the blood vessel walls of the microvasculature, formation of lymphoid and histiocytic infiltrates in the lungs, myocard, liver and kidneys, and dystrophic and necrotic changes in the parenchymal elements of these organs, which cumulatively indicated a morphological manifestation of an allergic reaction of DSR type. The study aimed to investigate some issues of the pathogenesis and pathomorphology of spontaneous Q fever infection in sheep.

Case Report Plasmablastic Lymphoma

Plasmablastic lymphoma (PBL) is a rare and aggressive subtype of non-Hodgkin lymphoma that commonly occurs in human immunodeficiency virus (HIV)–positive individuals and affects oral sites. The aim of this work was to report a case of a 57-year-old female patient diagnosed with HIV infection, presenting with a purplish exophytic lesion, which was bleeding, painful, friable, located in the maxilla, and affecting the alveolar ridge of teeth #23 to #27, hard palate, and vestibule. Panoramic radiography was performed. Initially, Kaposi sarcoma was suspected. However, after incisional biopsy and positive immunohistochemical reactions for Ki-67 (high expression), LCA, plasma cell, CD138, and EBER and negative reaction for CD20 and CD34, the diagnosis of PBL was established. The patient's health status deteriorated rapidly, and shortly after the receiving the results of the analyses, she died before initiation of cancer treatment.

Mediastinitis after cardiac procedures via median sternotomy: comparative analysis of outcomes

Aim. To compare the effectiveness of poststernotomy mediastinitis treatment in 41 patients who underwent vacuum-assisted closure or closed irrigation treatment. Methods. A retrospective analysis of 41 cases of sternal wound infection identified in patients who underwent cardiac surgery between 2007 and 2012. 18 patients (the first group) were treated using closed irrigation, 23 patients (the second group) - using vacuum-assisted closure. We compared the time interval for wound healing and drainage, serum levels of C-reactive protein and blood leukocyte counts on admission and at different time points until discharge. Results. In patients who were treated using vacuum-assisted closure, wound debridement and healing were achieved at shorter terms, and lower rate of complications were observed. There were 8 (44.4%) relapses requiring repeated surgery and debridement in the first group compared to 3 (13%, p=0.01) in the second group. C-reactive protein level decreased more rapidly in patients who were treated using vacuum-assisted closure (p 0.02). The duration of hospital stay was 67±4.1 days in the first group compared to 29.6±8.4 days in the second group (p=0.019). Moreover, patients who were treated using vacuum-assisted closure did not experience any significant discomfort and stayed active. Histological examination of the soft tissues showed marked lymphoid and plasma-cell reaction and neoangiogenesis by the end of the second week of vacuum-assisted closure. Conclusion. The use of vacuum-assisted closure shortens the term of wound debridement, granulating tissue formation and the duration of hospital stay compared to closed irrigation treatment.

Clinical and cerebrospinal fluid findings in lymphocytic meningo-radiculitis (Bannwarth's syndrome).

11 patients with lymphocytic meningo-radiculitis (Bannwarth's syndrome) are described. The disease is characterized by intensive pain, often radiating and migrating, and neurological deficits, i.e. peripheral facial palsies, as well as disseminated radiculopathies. In 4 patients the onset was preceded by an arthropod bite, close to which 3 patients exhibited an erythema chronicum migrans. In the cerebrospinal fluid there was a mononuclear pleocytosis, predominantely by lymphocytes. In the early stages, a plasma cell reaction was frequently encountered. Protein analysis indicated a defect in the blood brain barrier and an intrathecal synthesis of IgG. All patients recovered almost completely from their neurological symptoms within 1-2 months, irrespective of treatment.

Diagnostic challenges and standard therapy

In the diagnosis of multiple myeloma (MM), the clinician must exclude other disorders in which a plasma cell reaction may occur such as rheumatoid arthritis and connective tissue disorders, or metastatic carcinoma where the patient may have osteolytic lesions associated with bone metastases. Patients with smoldering multiple myeloma (SMM) or monoclonal gammopathy of undetermined significance (MGUS) have none of the complicating features of MM and do not require treatment with potentially toxic agents. The plasma cell labeling index can help make a differential diagnosis of MM from SMM. Patients with a high labeling index have a high risk of complications and should be monitored carefully. However, the labeling index can be low in active MM. In addition, SMM or MGUS patients have few or no circulating plasma cells. High-dose chemotherapy and stem cell support prolong overall survival in contrast to conventional therapy. If stem cell transplantation is considered, it is important to harvest the cells before using alkylating agents to obtain a sufficient number of cells. Supportive treatment consists of the occasional use of erythropoietin to maintain adequate hemoglobin levels and adequate hydration to protect renal function. Vaccination against pneumococcal infections and the prophylactic use of antibiotic therapy during the first 2 months of treatment can be beneficial. Recognizing the symptoms of spinal cord compression and initiating dexamethasone therapy promptly to prevent paraplegia are critical.

Memory B cells are biased towards terminal differentiation: a strategy that may prevent repertoire freezing.

Isolation of large numbers of surface IgD+CD38- naive and surface IgD-CD38- memory B cells allowed us to study the intrinsic differences between these two populations. Upon in vitro culture with IL-2 and IL-10, human CD40-activated memory B cells undergo terminal differentiation into plasma cells more readily than do naive B cells, as they give rise to five- to eightfold more plasma cells and three- to fourfold more secreted immunoglobulins. By contrast, naive B cells give rise to a larger number of nondifferentiated B blasts. Saturating concentrations of CD40 ligand, which fully inhibit naive B cell differentiation, only partially affect that of memory B cells. The propensity of memory B cells to undergo terminal plasma cell differentiation may explain the extensive extra follicular plasma cell reaction and the limited germinal center reaction observed in vivo after secondary immunizations, which contrast with primary responses in carrier-primed animals. This unique feature of memory B cells may confer two important capacities to the immune system: (a) the rapid generation of a large number of effector cells to efficiently eliminate the pathogens; and (b) the prevention of the overexpansion and chronic accumulation of one particular memory B cell clone that would freeze the available peripheral repertoire.

Autocrine and paracrine functions of cytokines in malignant lymphomas

Cytokines play important roles in the pathogenesis of lymphomas via an autocrine or a paracrine mechanism, or both. The characteristic clinical and histopathological features of malignant lymphomas may be due in part to elevated serum or tissue levels of cytokines. Determination of the effects of cytokines on the growth or differentiation of lymphoma cells is often complicated by the fact that more than one cytokine is responsible, and by the failure of anti-cytokine antibodies or antisense oligonucleotides to block the proliferation in vitro of lymphoma cells. However, it appears that IL-6 and/or IL-9 may play a prominent role in the tumor cell proliferation of Hodgkin's disease (HD), anaplastic large-cell lymphoma, or immunoblastic lymphoma. IL-6 may also be responsible for the plasmacytoid differentiation of lymphoma cells in polymorphic immunocytoma. The histopathological changes as a result of paracrine effects are most noticeable in HD. The malignant (H-RS) cells of HD have been shown to express IL-l, IL-5, IL-6, IL-9, TNF-α, M-CSF, TGF-β, and CD80, and, less frequently, IL-4 and G-CSF. These cytokines may be responsible for the increased cellular reaction and fibrosis observed in tissues involved by HD and for the immunosuppression found in patients with HD. In contrast to H-RS cells, most non-HD lymphoma cells do not produce cytokines in excess amounts and reveal only a minimal cellular reaction. Exceptions include T-cell-rich B-cell lymphoma, angiocentric T-cell lymphoma, and angio-immunoblastic lymphadenopathy (AILD)-like T-cell lymphoma. IL-4 is responsible for the T-cell reaction in T-cell-rich B-cell lymphoma, whereas IL-6 accounts for the plasma cell reaction in AILD-type T-cell lymphoma. The authors extensively review the role of cytokines in lymphomas because this may lead to major advances in the understanding of the molecular processes involved in the histopathogenesis of lymphomas.

Inflammatory Response in Retrieved Noncemented Porous-Coated Implants

One hundred forty-six noncemented porous-coated hip and knee implants retrieved from 97 patients were evaluated histologically for the type, amount, and anatomic distribution of tissue ingrowth. The degree of inflammatory cell infiltrate present was also evaluated and the predominant cell type was identified. An inflammatory infiltrate was present in the components of 21 of 97 patients (22%). In 16 of the 21 cases the infiltrate was lymphocytes and histiocytes with a minor population of plasma cells. One of the remaining five cases had a predominately plasma cell reaction, and the other four had significant populations of plasma cells. Vascular proliferation was observed in nine of the 21 cases. Bone ingrowth was present in ten of the 21 cases. A 38% incidence of removal for persistent pain was present in cases with an inflammatory infiltrate. Seventeen of 87 patients (20%) with cobalt-chromium devices and four of ten patients (40%) with titanium devices were identified as having an inflammatory infiltrate. The origin of the inflammatory infiltrate is unclear. All patients with inflammatory infiltrates had noninfected implants, which were not loose roentgenographically or clinically at the time of removal. Hypersensitivity and allergic responses to metal ions may produce such infiltrates. It is impossible, however, in the present study to definitively determine the etiology of the infiltrates.

Metallic wear in failed titanium-alloy total hip replacements. A histological and quantitative analysis.

We conducted extensive histological examination of the tissues that were adjacent to the prosthesis in nine hips that had a failed total arthroplasty. The prostheses were composed of titanium alloy (Ti-6Al-4V) and ultra-high molecular weight polyethylene. The average time that the prosthesis had been in place in the tissue was 33.5 months (range, eleven to fifty-seven months). Seven arthroplasties were revised because of aseptic loosening and two, for infection. In eight hips cement had been used and in one (that had a porous-coated implant for fifty-two months) no cement had been utilized. Intense histiocytic and plasma-cell reaction was noted in the pseudocapsular tissue. There was copious metallic staining of the lining cells. Polyethylene debris and particles of cement with concomitant giant-cell reaction were present in five hips. Atomic absorption spectrophotometry revealed values for titanium of fifty-sic to 3700 micrograms per gram of dry tissue (average, 1047 micrograms per gram; normal, zero microgram per gram), for aluminum of 2.1 to 396 micrograms per gram (average, 115 micrograms per gram; normal, zero micrograms per gram), and for vanadium of 2.9 to 220 micrograms per gram (average, sixty-seven micrograms per gram; normal, 1.2 micrograms per gram). The highest values were found in the hip in which surgical revision was performed at fifty-seven months. The concentrations of the three elements in the soft tissues were similar to those in the metal of the prostheses. The factors to which failure was attributed were: vertical orientation of the acetabular component (five hips), poor cementing technique on the femoral side (three hips), infection (two hips), and separation of a sintered pad made of pure titanium (one hip). A femoral component that is made of titanium alloy can undergo severe wear of the surface and on the stem, where it is loose, with liberation of potentially toxic local concentrations of metal debris into the surrounding tissues. It may contribute to infection and loosening.

The histology of reactive lymph nodes.

For histological evaluation of a lymph node specimen, it is essential to understand the morphology of the reaction patterns in the normal lymph node after challenge with antigen. The four different immunological reaction patterns seen in the lymph node each take place in their own compartment. Thus the follicle (or germinal) center cell reaction takes place in the follicle, the plasma cell reaction takes place in the medullary cords, the specific cellular response takes place in the paracortex, while in the sinuses, a histiocytic reaction may be observed. Often one reaction is followed or accompanied by another. Furthermore, because different antigenic challenges stimulate the four reactions in different ways, lymph node histology is highly variable and dependent on the kind of antigenic stimulation. Each of the four different reactions (and thus each of the four lymph node compartments) is described morphologically and immunohistologically. Markers identify the B-cell (follicle, medullary cords), T-cell (paracortex), or histiocytic (sinuses) nature of the compartments. A number of malignant conditions that can resemble benign lymph node lesions are discussed briefly, and morphologic and marker criteria for differential diagnosis are reviewed. Recognition of the four different reaction patterns with the addition of marker studies should allow a high percentage of accurate diagnoses.

Aplastic anaemia and the hypocellular myelodysplastic syndrome: histomorphological, diagnostic, and prognostic features.

In a retrospective study of 111 patients with aplastic anaemia iliac crest biopsies were evaluated for the presence of morphological features statistically related to the evolution of the disease. Prognostic variables for a transition to acute non-lymphatic leukaemia were: cellular atypias of the three haemopoietic lineages, as observed in the myelodysplastic syndrome, and especially "micromegakaryocytes"; high numbers or irregular distribution of megakaryocytes, or both; and (slight) marrow fibrosis. Clinical variables did not influence these prognostic correlations. Prognosis in relation to death from bone marrow failure without leukaemia might well have been influenced by a strong plasma cell reaction, but this correlation was weakened by clinical factors. On the basis of this study aplastic anaemia can thus be subdivided morphologically into two disease entities--namely, hypocellular myelodysplastic syndrome with a 23-82% risk of acute non-lymphatic leukaemia developing within three years, depending on how many variables associated with acute non-lymphatic leukaemia are present, and non-dysplastic myelohypoplasia.

Characterization of B-cell non-Hodgkin's lymphomas. A study using a panel of monoclonal and heterologous antibodies.

A panel of monoclonal and heterologous antibodies directed against clearly defined antigens was used to characterize the cellular composition of 57 non-Hodgkin's lymphomas, classified according to the Kiel classification, with a slight modification. The antisera were directed against T-lymphocytes and their subsets (Leu1, Leu2a, Leu3a, TA1), B-lymphocytes and their subsets (BA1, BA2, HLA-DR, CR1, sIg), macrophages (TA1, OKM1, anti-human monocyte 1, HLA-DR, CR1), dendritic reticulum cells (CR1, BA2, HLA-DR), interdigitating reticulum cells (HLA-DR, BA1) and Langerhans cells (OKT6, NA1/34). On the basis of the staining pattern of the neoplastic cells with the antibodies used and the nature and number of admixed cells, in particular T-cell subsets, dendritic reticulum cells and macrophages, the NHL could be divided into groups which correspond to the different diagnostic categories of the Kiel classification. Furthermore, the results underlined the existence of intermediate lymphocytic lymphoma as a separate diagnostic category. Histogenetically, the marker pattern of the neoplastic cells and the number and arrangement of the admixed cells are consistent with the view that at least two different lines of B-cell lymphomas can be recognized. One is related to the germinal centre cell reaction (to which B-lymphoblastic (Burkitt type), centroblastic, centroblastic/centrocytic, centrocytic, and intermediate lymphocytic lymphoma, and polymorphic immunocytoma belong) and the other is related to the plasma cell reaction (including chronic lymphocytic leucaemia and lymphoplasmacytoid immunocytoma), whereas B-immunoblastic lymphoma can originate from either line. Thus, polymorphic immunocytoma is a follicle centre cell lymphoma with differentiation into plasma cells rather than a lymphoplasmacytoid immunocytoma with blastic cells.

Germinal centers and the B-cell system. VI. Migration pattern of germinal-center cells of the rabbit appendix.

The migration pattern of germinal center cells of the rabbit appendix was studied and compared with that of appendix dome cells, spleen cells, thymus cells and thoracic duct lymphocytes. To discriminate T- and B-cell migration pathways, normal or T-cell-depleted rabbits were used as donors. Cell suspensions were labeled in vitro with 3H-leucine followed by intravenous transfer. The migration of labeled cells in lymphoid organs was studied using autoradiography, particular attention being paid to the spleen of the recipient. B-cells from the appendix dome, spleen and thoracic-duct lymph migrate to primary follicles or the corona of secondary follicles via thymus-dependent areas of peripheral lymphoid organs. In contrast, a B-cell subpopulation from the germinal centers of the appendix migrates to the center of splenic primary follicles and into germinal centers. The migration of germinal center cells to splenic follicle centers is not enhanced by specific antigens. The migration properties of B-cells, possibly changing during differentiation, may be instrumental in the two types of immune reactions, i.e., plasma-cell reaction and germinal-center reaction.

A T-dependent plasma cell response: part of a graft-versus-host and host-versus-graft reaction in the rabbit spleen.

B-cell reactivity, as expressed in a plasma cell reaction may be part of a graft-versus-host or host-versus-graft reaction. Cell transfer experiments were able to prove this. Histological evidence is presented for the occurrence of the so-called "allogeneic effect" during a graft-versus-host or host-versus-graft reaction in the rabbit spleen. Cell suspensions containing both T- and B-cells give rise to a cellular and a humoral immunity reaction component upon transfer to histoincompatible recipients. This can also occur during a graft-versus-host reaction. This B-cell response is T-cell dependent.

Immunohistologic analysis of the organization of normal lymphoid tissue and non-Hodgkin's lymphomas.

Hoping to improve the systems for identifying and classifying normal and malignant lymphoid subpopulations, frozen and paraffin sections of nonmalignant lymphoid tissue and of malignant lymphomas were immunostained for surface (S) and cytoplasmic antigens using the peroxidase-antiperoxidase method. Primary follicle cells and follicle mantle cells known to be part of the recirculating B-cell pool were found to be constantly Ia and C3 receptor (C3R) positive, mostly SIgM and SIgD positive and cytoplasmic immunoglobulin (CIg) negative. The light zone of germinal centers (GC), which is rich in centrocytes, contained a large number of T cells and showed the well-known intercellular Ig network pattern; the dark zone, containing densely packed centroblasts, was usually free of T cells, but was bordered ay a mantle-like accumulation of T cells. Usually only some of the GC cells were definitely positive for SIg and CIg of different classes. All cells reacted positively for Ia and C3R. In areas described by other authors as containing marginal zone cells, cells densely bearing SIgM and deficient in SIgD were detected. The immunoblasts of the hyperplastic plasma cell reaction usually contained CIg. Cells from chronic lymphoid leukemia sections that immunostained for SIgM and SIgD were interpreted as representing a neoplasm of recirculating B cells expressing SIgM and SIgD. The immunohistologic architecture of follicular centroblastic/centrocytic lymphoma showed a more or less close similarity to the organization of secondary follicles. Lymphomas whose cells resembled reactive centrocytes were strongly SIgM positive and SIgD negative or only weakly SIgD positive. CIg was demonstrable in nearly 90% of the lymphomas whose cells resembled centroblasts and in 70% of the lymphomas whose cells resembled immunoblasts of the plasma cell reaction. Finally, immunohistologic staining results from a T-zone lymphoma are presented, which confirm that this lymphoma was composed of a neoplastic T zone and a non-malignant B zone.

Synovial pathologic changes in spontaneous canine rheumatoid-like arthritis.

The synovial fluid and membrane were studied in 10 dogs meeting the American Rheumatism Association criteria for classic human rheumatoid arthritis (RA). Light microscopic pathologic features were consistent with those found in the human disease. Neutrophilic infiltration of synovium was somewhat more prominent than in chronic human RA, and activated lymphocytes in fluid or membrane were less frequent. The proliferative and plasma cell reaction seemed identical. Electron microscopy (EM) suggested microvascular injury with findings which included electron dense deposits in the vessel walls of 2 dogs. Seven dogs had meshworks of 20‐25 mm tubules in tubuloreticular structures (TRS) similar to those seen in human systemic lupus erythematosus and only occasionally in human RA. There were also crystalline arrays of tubules, a configuration previously reported in tumors and virus infections and possibly suggestive of a cellular reaction to virus infection. To date no initiating agent has been identified, but this spontaneous canine disease which is very similar to human RA can provide a valuable model in which to examine pathogenesis of chronic arthritis.