Majority Of Lymph Nodes Research Articles

Comparison of Sample Adequacy and Diagnostic Yield of the 21-G and 25-G EBUS TBNA Needles.

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS TBNA) of mediastinal lymphadenopathy has been shown to be equivalent and possibly even superior to mediastinoscopy. Since the original dedicated 22-G aspiration needle, 21-G, 25-G, and recently 19-G needles have been introduced. Smaller needles may be more flexible and adept at accessing more difficult nodes, and may have less blood contamination compared with larger needles. This is a prospective observational study of 50 consecutive patients who underwent endobronchial ultrasound-guided transbronchial needle aspiration with a 21-G needle and a 25-G needle for a total of 100 biopsies. The study slides were examined by a dedicated lung cytopathologist, who was blinded to the needle size used for each slide. Demographic data, and lymph node size were recorded. Comparisons between the 2 needles with regards to sample adequacy and diagnostic yield was performed using the McNemar test for dichotomous variables and marginal homogeneity test for nondichotomous variables since samples were related. The majority of lymph nodes (96%) were at least >1 cm. Adequate specimens were obtained in 78% of cases with the 21-G needle and 86% of cases with 25-G needle (P-value=0.424). The overall diagnostic yield was 74% and 80% with the 21-G needle and 25-G needle, respectively (P-value=0.607). Our study demonstrates that the there is no difference in terms of specimen adequacy and diagnostic yield when the 25-G needle is compared with the 21-G needle.

Can Ex Vivo Magnetic Resonance Imaging of Rectal Cancer Specimens Improve the Mesorectal Lymph Node Yield for Pathological Examination?

The aim of this study was to use 7 T ex vivo magnetic resonance imaging (MRI) scans to determine the size of lymph nodes (LNs) in total mesorectal excision (TME) specimens and to increase the pathological yield of LNs with MR-guided pathology. Twenty-two fixated TME specimens containing adenocarcinoma were scanned on a 7 T preclinical MRI system with a T1-weighted 3-dimensional gradient echo sequence with frequency-selective lipid excitation (repetition time/echo time, 15/3 milliseconds; resolution, 0.293 mm) and a water-excited 3-dimensional multigradient echo (repetition time, 30 milliseconds; computed echo time, 6.2 milliseconds; resolution, 0.293 mm) pulse sequence.The first series of 11 TME specimens (S1) revealed the number and size of LNs on both ex vivo MRI and histopathology. The second series of 11 TME specimens (S2) was used to perform MR-guided pathology. The number, size, and percentages of yielded LNs of S1 and S2 were compared. In all specimens (22/22), a median number of 34 LNs (interquartile range, 26-34) was revealed on ex vivo MRI compared with 14 LNs (interquartile range, 7.5-21.5) on histopathology (P = 0.003). Mean size of all LNs did not differ between the 2 series (ex vivo MRI: 2.4 vs 2.5 mm, P = 0.267; pathology: 3.6 vs 3.5 mm, P = 0.653). The median percentages of harvested LNs compared with nodes visible on ex vivo MRI per specimen for both series were not significantly different (40% vs 43%, P = 0.718). By using a size threshold of greater than 2 mm, the percentage improved to 71% (S1) and to 78% (S2, P = 0.895). The median number of harvested LNs per specimen did not increase by performing MR-guided pathology (S1, 14 LNs; S2, 20 LNs; P = 0.532). Ex vivo MRI visualizes more LNs than (MR-guided) pathology is able to harvest. Current pathological examination was not further improved by MR guidance. The majority of LNs or LN-like structures visible on ex vivo MRI below 2 mm in size remain unexplained, which warrants a 3-dimensional approach for pathological reconstruction of specimens.

Reliability of sonoelastography in predicting pediatric cervical lymph node malignancy

Controversy exists as regards the best non-invasive diagnostic tool for pediatric cervical lymphadenopathy. The current work aimed to evaluate the reliability, sensitivity, specificity, and accuracy of sonoelastography in diagnosing benign and/or malignant pediatric cervical lymphadenopathy. Prospective study took place over a period of 4years from January 2013 to December 2016. A total of 177 lymph nodes (LNs) in 128 children with an age ranging from 11months to 12years were recruited in this study. Patients were 77 males and 51 females with a ratio of 3:2. All patients underwent a thorough history taking and clinical examination of the neck focusing on the cervical lymph nodes. After that, a B-mode sonography, Color Doppler ultrasound, and Sonoelastography were performed. Elastographic patterns of 1-5 were evaluated, whereas patterns of 3-5 (firm to hard) were suspected to have a malignant nature. Sonographic-guided aspiration cytology took place in 107 lymph nodes and excisional biopsy in 102 lymph nodes, whereas 13 lymph nodes responded adequately to conservative treatment. They proved to be benign reactive hyperplasia. The majority of LNs (87%) were of the malignant type that showed an elastographic pattern of 3-5. The same patterns were observed in only 6 (3.4%) of the benign LNs. Sonoelastography showed a sensitivity of 85.9%, specificity of 100%, PPV of 100%, NPV of 75.96%, and overall accuracy of 90.23% in distinguishing benign from malignant lymph nodes. Using the B-Mode ultrasound, an abnormal hilum was seen in 75%. The accuracy of color Doppler US reached 82.7%. Sonoelastography may be superior to other US modalities in elucidating different cervical lymph node biopsy helping to distinguish benign from malignant lesions. This may replace the lymph node biopsies in the future. Moreover, its use in the follow-up of patients with cervical malignancies may reduce the number of future biopsies. Further studies with more patients may be needed for a better assessment of results.

Abstract 1993: Rapid clonal evolution of dormant micrometastatic disease in head and neck cancer

Abstract Head and neck cancer (HNC) is prone to locoregional recurrence which results in poor clinical outcome. Recent HNC clinical studies demonstrated that cervical lymph node dissection results in improved patient outcome even in early disease. These results suggest that dormant micrometastatic cancer occurs early in head and neck carcinogenesis. We used our established in vivo chemical carcinogenesis model of head and neck cancer to characterize dormant micrometastatic disease using genetic lineage tracing and null mutant mice. Histopathology was analyzed by hematoxylin and eosin staining. Telomere DNA damage response was determined by immunofluorescent 53BP1 localization at telomeres, and by ATM/ATR western blotting. Keratin expression and proliferation index were determined by immunohistochemistry. Apoptotic cells were determined by TUNEL analysis. Telomerase activity was determined by telomere repeat amplification protocol. Alternative lengthening of telomeres was determined by PML localization at telomeres, telomere circular DNA analysis, and chromosome orientation fluorescence in situ hybridization. Genomic instability was determined by high throughput sequencing. Cancer stem cells were sorted by flow cytometry and transplanted subcutaneously in Matrigel. Advanced HNC exhibited significant metastatic disease in the majority of lymph nodes. Early HNC and even premalignant lesions exhibited micrometastatic disease in most lymph nodes. These micrometastatic lesions contained multiple HNC clones that were dependent for proliferation on paracrine chemokine signaling from a tumorigenic keratin 15+ cancer stem cell population. In situ, the micrometastatic K15+ cancer stem cell population exhibited increased telomere DNA damage response including activated ATM and ATR which correlated with low proliferation index. Clonal evolution of K15+ micrometastatic cancer stem cells was dependent on extremely short telomeres. These cells expressed both telomerase and recombination-based alternative lengthening of telomeres (ALT) activities. K15+ micrometastatic cancer stem cells exhibited high levels of genomic instability resulting from telomere fusions and expressed metastasis-specific gene expression programs. These patterns of micrometastatic gene expression revealed targeted therapeutic vulnerabilities. These results indicate that dormant micrometastatic disease develops rapidly during head and neck carcinogenesis from normal epithelial cells with short telomeres and is sensitive to targeted therapies. Citation Format: Angelica M. Lagunas, Jianchun Wu, David L. Crowe. Rapid clonal evolution of dormant micrometastatic disease in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1993.

Computed tomographic appearance of abdominal lymph nodes in healthy cats.

BackgroundComputed tomography (CT) is commonly used in veterinary medicine and plays an important role in disease identification and cancer staging. Identification of abnormal abdominal lymph nodes is important for clinical, therapeutic, and prognostic decision making. No published study describes the CT appearance of abdominal lymph nodes in healthy cats.Hypothesis/ObjectivesAll abdominal lymph centers will be identified on CT with the majority of lymph nodes being elongated and homogenously contrast enhancing.AnimalsSixteen healthy cats without clinical or biochemical evidence of disease.MethodsPrecontrast and postcontrast CT images of sedated healthy cats were used to identify the presence and descriptive characteristics of intra‐abdominal lymph nodes. These assessments then were compared with patient characteristics to identify possible correlations.ResultsAbdominal lymph nodes were readily identified on CT with caudal mesenteric, colic, hepatic, inguinal, and pancreaticoduodenal lymph nodes identified in 16/16 cats. Lymph node size and shape varied among lymph centers with nearly all lymph nodes homogeneously contrast enhancing in 515/525. Significant negative correlations were identified between age and length (P = .0166) and width (P = .0387) of abdominal lymph nodes as well as age and number of sacral lymph nodes (P = .0493). Intranodal fat was present in 18/525 lymph nodes.Conclusions and Clinical ImportanceCT readily permitted identification and characterization of feline abdominal lymph nodes. This study provides subjective and objective data on the CT characteristics of abdominal lymph nodes in 16 healthy cats, with younger cats having larger abdominal lymph nodes and a higher number of sacral lymph nodes.

The expression profiles of the galectin gene family in primary and metastatic papillary thyroid carcinoma with particular emphasis on galectin-1 and galectin-3 expression

IntroductionGalectin family members have been demonstrated to be abnormally expressed in cancer at the protein and mRNA level. This study investigated the levels of galectin proteins and mRNA expression in a large cohort of patients with papillary thyroid carcinoma and matched lymph node metastases with particular emphasis on galectin-1 and galectin-3. MethodsmRNA expression of galectin family members (1, 2, 3, 4, 7, 8, 9, 10 and 12) were analysed by real-time polymerase chain reaction in 65 papillary thyroid carcinomas, 30 matched lymph nodes with metastatic papillary thyroid carcinoma and 5 non-cancer thyroid tissues. Galectin-1 and 3 protein expression was determined by immunohistochemistry in these samples. ResultsSignificant expression differences in all tested galectin family members (1, 2, 3, 4, 7, 8, 9, 10 and 12) were noted for mRNA in papillary thyroid carcinomas, with and without lymph node metastasis. Galectin-1 protein was more strongly expressed than galectin-3 protein in papillary thyroid carcinoma. Galectin-1 protein was found to be overexpressed in 32% of primary papillary thyroid carcinomas. A majority of lymph nodes with metastatic papillary thyroid carcinoma (53%) had significantly increased expression of galectin-1 protein, as did 47% of primaries with metastases. Galectin-1 mRNA levels were decreased in the vast majority (94%) of primary thyroid carcinomas that did not have metastases present. Galectin-3 protein levels were noted to be overexpressed in 15% of primary papillary thyroid carcinomas. In primary papillary thyroid carcinoma with lymph node metastases, 32% had over expression of galectin-3 protein. Overexpression of galectin-3 mRNA was noted in 58% of papillary thyroid carcinomas and 64% of lymph nodes bearing metastatic papillary thyroid carcinoma. Also, primary papillary thyroid carcinoma with lymph node metastases had significantly higher expression of galectin-3 mRNA compared to those without lymph node metastases. ConclusionGalectin family members show altered expression at the mRNA level in papillary thyroid cancers. Overexpression of galectin-1 and 3 proteins were noted in papillary thyroid carcinoma with lymph node metastases. The results presented here demonstrated that galectin-1 and galectin-3 expression have important roles in clinical progression of papillary thyroid carcinoma.

Size distribution and metastasis in discarded intrapulmonary lymph nodes (LN) after lung cancer resection.

7072^ Background: Lymph node (LN) status is the most important prognostic determinant after resection of lung cancer. 18% of a SEER cohort and 12% of a Memphis cohort had no LNs examined (pNx). Patients with pNx have inferior survival to T-category matched pN0 patients with at least 1 LN examined. The optimal number of LN needed to safely declare a patient pN0 may be >10. Less than 20% of resections in SEER achieve this. We hypothesized that a significant number of intrapulmonary LNs are left unexamined and some may harbor metastatic disease. We report the size characteristics of materials examined in a re-dissection protocol to test this hypothesis. Methods: Prospective study of lung resection specimens re-dissected after signout of the final pathology report. Remnant lung material was dissected with thin cuts and all LN-like material was retrieved for microscopic examination, irrespective of size or location. The size of non-LN tissue, LN without metastasis and LN with metastases were compared using the Wilcoxon-Mann-Whitney test. Results: 112 specimens were examined and 1,094 LN-like materials were retrieved. 749 (69%) proved to be LN tissue. 71 (10%) LNs retrieved had metastasis. Non-LN tissue was significantly smaller than LN tissue (p<0.0001). LNs with metastasis were significantly larger than those without metastasis (p <0.0001). 60% of materials >2cm were LNs with metastasis. 7% of materials <1cm were LN with metastasis. 52% of LNs with metastasis, and 55% of LNs without metastasis measured from 0.5 to 1.5cm (Table). Majority of LNs >2cm had metastatic disease, but 40% did not; a notable proportion of LNs with metastasis were small. Nearly equal percentages of LNs with and without metastasis were found in the range of 0.5-1.5cm. Conclusions: Statistical differences in size between lymph nodes with and without metastasis is clinically meaningless due to broad overlap. LN size alone is not an adequate predictor of LN metastasis. [Table: see text]

Tumor micrometastases in mesorectal lymph nodes and their clinical significance in patients with rectal caner.

To investigate the number, size, and status of lymph nodes within the mesorectum and to explore the prognostic significance of lymph node micrometastases in patients with rectal cancer. Thirty-one patients with rectal cancer undergone total mesorectal excision between October 2001 and October 2002 were included. Mesorectal nodes retrieved from the resected specimens were detected with a combination of haematoxylin and eosin (HE) staining and immunohistochemistry (IHC). The relations between lymph node metastases, micrometastases and postoperative recurrence were analyzed. A total of 548 lymph nodes were harvested, with 17.7+/-8.2 nodes per case. The average number of metastatic nodes in HE-positive patients and micrometastatic nodes in IHC-positive patients was 5.2+/-5.1 per case and 2.2+/-1.3 per case, respectively. The mean size of all nodes and metastatic nodes was 4.1+/-1.8 mm and 5.2+/-1.7 mm in diameter, respectively. The mean size of micrometastatic nodes was 3.9+/-1.4 mm in diameter. The size of the majority of mesorectal nodes (66.8%), metastatic nodes (52.6%), and micrometastatic nodes (79.5%) was less than 5 mm in diameter. During a median follow-up period of 24.6+/-4.7 mo, 5 patients (16.7%) had recurrence, of them 2 died and 3 survived. Another case died of tumor unrelated cause and was excluded. All 5 recurrent cases had 3 or more nodes involved, and one of them developed only lymph node micrometastases. The mean number of both metastatic and micrometastatic nodes per case differed significantly between the recurrent and non-recurrent groups (P<0.01 and P = 0.01, respectively). The majority of lymph nodes, metastatic, and micrometastatic lymph nodes within the mesorectum are smaller than 5 mm in diameter. The nodal status and the number of lymph nodes involved with tumor metastases and micrometastases are related to the rapid postoperative recurrence.

Lymphocytes from lymph nodes at different distances from human melanoma vary in their capacity to inhibit/enhance tumor cell growth in vitro

Eighty-six lymph nodes at measured distances from a primary tumor were removed from 68 patients with malignant melanoma. The ability of lymph-node lymphocytes (LNL) from these nodes to modulate proliferation of a melanoma cell line (UCLA-SO-M14) in vitro was tested. LNL from the majority of lymph nodes (66%) inhibited M14 growth, but LNL from 34% of nodes stimulated growth of the cell line. Peripheral blood mononuclear cells always inhibited M14 growth. Distance of a node from the primary tumor was found to be an important determinant of LNL activity. This was demonstrated using pairs of nodes from individual patients. In 86% of cases, LNL from nodes located nearer to the tumor inhibited M14 growth less than LNL from more distant nodes. Stimulation of M14 growth was commonest with LNL from nodes located near to the tumor. CD8+ T cells were largely responsible for M14 growth inhibition, whereas CD4+ cells were associated with stimulation of M14 growth. Removal of CD4+ lymphocytes from growth stimulatory LNL resulted in a CD4-depleted LNL preparation that inhibited M14 cell proliferation. The environment in lymph nodes located dose to tumors may thus favor growth of metastatic tumor cells.

Utility of mapping lymph nodes cleared from rectal adenocarcinoma specimens

The lymph node clearing technique improves the detection of lymph nodes in colorectal cancer specimens. The purpose of this study was to determine the utility of mapping the lymph nodes cleared from rectal adenocarcinoma specimens by evaluating the possible relationship between the pattern of lymph node metastases to the site of the recurrent disease. A retrospective medical record review was performed in 40 patients with primary rectal adenocarcinoma. The specimens were analysed by lymph node clearing technique and mapped after surgery. The lymph nodes were mapped according to their location in the cleared specimens. Statistical analysis was performed using the chi 2-test. A total of 1290 lymph nodes were cleared in 40 specimens. Of these, 1126 (87%) lymph nodes were < or = 5 mm. One-hundred and ten (9%) lymph nodes were metastatic. Sixty-seven (61%) of these 110 lymph nodes were 5 mm or less in size. The majority of lymph nodes with or without metastases were in the pelvis, as opposed to an extrapelvic location (P = 0.0001). Eleven patients recurred. In nine of these patients the recurrence showed a direct relationship between the level of metastatic lymph node location (pelvic vs. extrapelvic) and the site of the recurrent disease (loco-regional or systemic, P = 0.05). The majority of lymph nodes, both normal and metastatic, cleared from specimens from rectal adenocarcinoma were < or = 5 mm in diameter. The lymph node mapping technique may help in predicting the site of recurrence.

Detection of Epstein-Barr virus DNA in Hodgkin- and Reed-Sternberg-cells by single cell PCR.

The Epstein-Barr virus (EBV) can be detected in the majority of lymph nodes involved by Hodgkin's lymphoma using the highly sensitive polymerase chain reaction (PCR). However, the rate of EBV-DNA detection by in-situ hybridisation, which allows allocation of EBV to a defined cell population, i.e. the neoplastic H&RS-cells, is lower. In an attempt to combine the advantages of the high sensitivity of the PCR and the possibility of cellular allocation by in-situ hybridisation, we established a single-cell PCR of Hodgkin- and Reed-Sternberg (H&RS)-cells isolated by micromanipulation from biopsy tissues. We amplified EBV sequences from the BamW-region by single-cell PCR. Using this method we were able to detect EBV-DNA in the H&RS-cells from 4 of 6 patients. In EBV positive cases all H&RS-cells of a given patient were positive, proving the high sensitivity and reproducibility of the method. Other cells in the biopsy tissue involved by EBV-positive H&RS-cells were shown to be negative. This indicates that EBV may have a role in the pathogenesis of many but not all cases of Hodgkin's disease.

Hen egg-white lysozyme-specific T cells elicited in hen egg-white lysozyme-transgenic mice retain an imprint of self-tolerance.

The characteristics of T cell self-tolerance were examined in hen egg-white lysozyme (HEL)-transgenic (Tg) mice that were tolerant to a dose of HEL that was immunogenic in non-Tg littermates. HEL-specific T cells were identified in the periphery of the Tg mice after immunization with 100-times more HEL than was required to achieve a response in normal littermates. The Tg T cells were functional in vivo as they were capable of providing help to generate a HEL-specific antibody response. Selective deletion of T cells specific for the dominant T cell determinant of the native protein was not the primary mechanism of T cell tolerance in the HEL-Tg mice because, similar to non-Tg littermates, the majority of lymph node (LN) and T cell clones from HEL-Tg mice were specific for the dominant T cell determinant of HEL. Rather, our findings support the idea that the HEL-reactive T cells were anergic in vivo, but could be partially activated with a strong stimulus to the immune system (i.e., 20 nmol HEL and CFA). This conclusion is based on three observations: 1) proliferation in vitro to HEL by Tg LN T cells was subnormal (25% of control) and required 2 log more Ag to proliferate when compared with proliferation of LN from non-Tg littermates; 2) T cell clones isolated from HEL-Tg mice also proliferated poorly upon stimulation with HEL and Con A, although lymphokine production from the same stimuli was similar to that obtained from non-Tg clones; 3) invariably, upon repeated antigenic stimulation in vitro, the Tg T cell clones acquired full proliferative capacity to Ag and mitogens.

Characterization of the immune response to a secondary encephalitogenic epitope of basic protein in Lewis rats. II. Biased T cell receptor V beta expression predominates in spinal cord infiltrating T cells.

The immune response of Lewis rat lymph node T cells to guinea pig myelin basic protein (GP-BP) in experimental allergic encephalomyelitis is directed primarily against a region of basic protein encompassed by residues 72-89. T cells that respond to this epitope are restricted by the RT1.B class II molecule of the MHC and use V beta 8.2 exclusively in their TCR. A second region of GP-BP, residues 87-99, also induces experimental allergic encephalomyelitis in Lewis rats but this response is restricted primarily by RT1.D. Elsewhere we describe the biologic characteristics of T cell clones responding to the synthetic peptide, s87-99, and to a related peptide, s85-99. We present a detailed analysis of TCR V beta gene expression among these clones, derived from the lymph node and spinal cord of immunized animals, and among spinal cord derived T cell clones reactive to GP-BP 72-89. We find that spinal cord-derived clones, reactive to s85-99 and to s87-99, use V beta 6 predominantly. In contrast, T cell clones derived from lymph nodes and reactive to the same peptides express multiple V beta genes including V beta 6. This difference in heterogeneity of V beta usage at the clonal level is also seen in T cell lines derived from spinal cord and immune lymph node. DNA sequence comparison of the CDR3 regions in V beta 6+ spinal cord clones revealed a conserved amino acid motif also found in the majority of V beta 6 sequences from the spinal cord anti-s85-99 line. Although V beta 6 was expressed in some lymph node-derived clones, only one contained a CDR3 region similar to that seen in spinal cord isolates. All spinal cord-derived T cell clones reactive to GP-BP 72-89 used V beta 8.2 and most (five of six) contained the AspSer residues in CDR3 previously shown to be associated with V beta 8.2 receptors expressed by the majority of lymph node T cells responding to GP-BP 72-89. These data indicate that TCR V beta usage in peripheral T cells responding to an autoantigen does not always predict the V beta usage among T cells at the site of an autoimmune attack. Possible explantations for the relative homogeneity in TCR V beta expression seen in T cell clones derived from the spinal cord are discussed.

Occurrence and patterns of muramidase containing cells in Hodgkin's disease, non-Hodgkin's lymphomas, and reactive hyperplasia

The occurrence and pattern of cytoplasmic muramidase containing histiocytes were studied by the unlabeled antibody peroxidase-antiperoxidase method in biopsy material from patients with Hodgkin's disease, non-Hodgkin's lymphomas, and reactive hyperplasia. The majority of lymph nodes from patients with Hodgkin's disease, nodular lymphoma, and reactive hyperplasia gave positive staining reactions when tested in this manner. Differences in the staining pattern were observed for the different conditions studied. In general, stain positive cells occurred in one of the following four patterns: nodular, dispersed, aggregating without background stain, or aggregating with background stain (mottling pattern). The nodular and aggregating without background stain patterns were not specific and were seen in various conditions. The dispersed pattern, however, was observed only in some cases of non-Hodgkin's diffuse lymphomas, suggesting a subgroup of tumors characterized by active participation of reactive histiocytes. The mottling pattern was virtually limited to Hodgkin's disease. Since the mottling pattern appeared to be produced by virtue of a large amount of extracellular muramidase, the elevation of the serum muramidase level in Hodgkin's disease may be related to enzymatically active secretory histiocytes. Moreover, the mottling staining pattern was observed frequently in the lymphocytic predominance and nodular sclerosis type of Hodgkin's disease, but relatively infrequently in the mixed cellularity or lymphocytic depletion types, suggesting that the variation in histiocytic activity may be related to the course of the disease. The decreased staining reaction observed in the latter two categories could not be accounted for by a decrease in the numbers of histiocytic cells in hematoxylin and eosin stained sections, suggesting that release or synthesis may be defective in those unfavorable types of Hodgkin's disease.

THE SELECTIVE IRRADIATION OF CANINE LYMPH NODES BY MEANS OF INTRALYMPHATIC INJECTION OF 32P

Intralymphatic injection of radioactive chromic phosphate produced a severe destruction of a majority of lymph nodes, and subsequent marked lymphopenia in dogs. Selectivity of radiation was evidenced by histological study of other major organs and blood counts. Antibody production of these animals against human serum albumin was significantly inhibited; however, the reactivity to the allografted heart was not altered.