Meal induced increase in serum triglycerides has no effect on lymphocyte response to mitogens

The effect of a standardized heavy meal on the lymphocyte transformations induced by phytohaemagglutinin (PHA), concanavalin A (Con A) and PPD tuberculin was studied. The meal significantly increased the serum triglycerides (P less than 0.01), while it had no effect on cholesterol or high density lipoprotein-cholesterol levels. The increase in serum triglycerides did not affect lymphocyte transformation induced by phytohaemagglutinin or concanavalin A in whole blood microcultures. A slight decrease was observed when lymphocytes were stimulated with one out of three concentrations of PPD tuberculin (P less than 0.05). However, there was no correlation with the increase of triglycerides and decrease in lymphocyte transformation. Our observation shows that physiological changes in serum triglycerides do not affect the capacity of lymphocytes to respond to mitogenic stimulation, and the whole blood micromethod for lymphocyte stimulation to screen the capacity of cell-mediated immunity does not depend on the meal schedule of the patients.     

A method for coupling protein antigens to erythrocytes. II. Use of the method in the diagnosis of tuberculosis

A serological technique, using formalinized red cells coupled to tuberculin PPD as antigen, has been assayed in a trial series of 124 tuberculous and 139 non-tuberculous patients. The stability of the antigen preparation, and the omission of an adsorption procedure for the removal of isoagglutinins facilitated the performance of the test. The results indicate that the technique warrants further trial as a diagnostic criterion of infection tuberculosis.     

A 180-kilodalton protein from Mycobacterium tuberculosis defined by a human T cell clone

A high molecular weight protein from Mycobacterium tuberculosis (M. tuberculosis) has been identified, that is recognized by peripheral blood mononuclear cells from several tuberculous patients and by a T cell clone derived from a patient with tuberculous pleurisy. Purification of this fraction demonstrated biological activity to reside in a 180-kDa protein component. This mycobacterial protein appears to exist in some, but not all mycobacteria as the clone reacts to M. tuberculosis, BCG M. kansasii, M. flavescens and M. fortuitum, but not to M. intracellulare, M. scrofulaceum or a variety of gram-positive or gram-negative bacteria, or to PPD. Specific anti-genic challenge of the T cell clone in the presence of irradiated antigen presenting cells results in proliferation and interleukin-2 (IL-2) production. Proliferation is restricted to HLA Class II antigens as antigenic recognition occurs only in the presence of either one of the two parental DR haplotypes. Peripheral blood mononuclear cells from several other patients with pulmonary tuberculosis also proliferate in response to this antigen, emphasizing the relevance of T cell cloning techniques in identifying important mycobacterial antigens.     

HLA B27 and defects in the T-cell system in Whipple''s disease

The cellular immune system was tested in nine patients with Whipples' disease. Three patients had active disease, and six had been in remission for up to 10 years. Intradermal delayed hypersensitivity reactions to candidin, trichophytin, tuberculin and varidase, T-cell counts as determined by E-rosettes, allogeneic stimulation of lymphocytes in the mixed lymphocyte culture, and mitogenic activation of lymphocytes by concanavalin A, phytohaemagglutinin and by pokeweed mitogen, were tested in the patients and compared with control subjects. HLA typing was performed in all patients. The reaction to tuberculin and varidase, the T-cell counts and the activation of lymphocytes by concanavalin A were significantly reduced in patients with active disease and in patients during remission. The reaction to candidin and trichophytin was poor even in the controls. The mean results of the mixed lymphocyte culture, phytohaemagglutinin, and pokeweed mitogen activation tests were not significantly different from the controls. In patients with active disease the mixed lymphocyte culture reaction and the T-cell counts were less than in patients in remission. The results suggest a persistent defect of T-cells in patients with Whipple's disease, a defect that is more severe in patients with active disease. The finding of HLA B27 in four of thenine patients supports the hypothesis of primary rather than secondary impairment of the cellular immune system in Whipple's disease.     

T细胞斑点试验AB抗原检测结果对结核感染患者诊断意义探讨

目的探讨结核感染T细胞斑点试验(T-SPOT.TB)中AB两种抗原检测结果在临床结核感染患者诊断中的意义。方法选取2013年6~11月住院治疗并最终确诊活动性结核的96例患者为研究对象,采集其外周血进行T-SPOT.TB检测,将检测结果与结核菌素试验(PPD)及最终诊断结果进行对比,并对AB两种抗原检出结果的一致性及其阳性斑点分布特点进行分析。结果 T-SPOT.TB灵敏度为97.9%,特异度为87.8%,准确度为94.5%,阳性预测值(PPV)为94.0%,阴性预测值(NPV)为95.6%,均显著高于PPD检测结果(P0.01)。T-SPOT.TB两种抗原A和B对检测结果阳性率无统计差异,阳性斑点分布特征分析显示抗原A阳性斑点数与结核活动性呈正相关趋势,有较高的特异度;而抗原B则分别在高、低阳性斑点区呈现活动性结核检出的高峰,具有更好的敏感度。结论 T-SPOT.TB试验对活动性结核诊断有高度的敏感度和特异度,且AB两种抗原表现出不同的阳性检出规律和意义。T-SPOT.TB试验可为临床结核病的筛查和大规模流行病学调查提供新的技术分析手段。     

IL-10-producing T cells suppress immune responses in anergic tuberculosis patients

The lethality of Mycobacterium tuberculosis remains the highest among infectious organisms and is linked to inadequate immune response of the host. Containment and cure of tuberculosis requires an effective cell-mediated immune response, and the absence, during active tuberculosis infection, of delayed-type hypersensitivity (DTH) responses to mycobacterial antigens, defined as anergy, is associated with poor clinical outcome. To investigate the biochemical events associated with this anergy, we screened 206 patients with pulmonary tuberculosis and identified anergic patients by their lack of dermal reactivity to tuberculin purified protein derivative (PPD). In vitro stimulation of T cells with PPD induced production of IL-10, IFN-gamma, and proliferation in PPD(+) patients, whereas cells from anergic patients produced IL-10 but not IFN-gamma and failed to proliferate in response to this treatment. Moreover, in anergic patients IL-10-producing T cells were constitutively present, and T-cell receptor-mediated (TCR-mediated) stimulation resulted in defective phosphorylation of TCRzeta and defective activation of ZAP-70 and MAPK. These results show that T-cell anergy can be induced by antigen in vivo in the intact human host and provide new insights into mechanisms by which M. tuberculosis escapes immune surveillance.     

Relationship between whole-blood interferon-gamma production and extent of radiographic disease in patients with pulmonary tuberculosis

The aim of this study was to determine whether whole-blood interferon-gamma (IFN-gamma) production correlates with the radiographic extent of pulmonary tuberculosis before treatment. The subjects were 40 human immunodeficiency virus-negative patients with pulmonary tuberculosis and 36 healthy volunteers. The concentrations of IFN-gamma in whole blood stimulated with Mycobactrium tuberculosis purified protein derivatives (tuberculous PPD) and phytohemagglutinin (PHA) were evaluated. PHA-stimulated IFN-gamma (PHA-IFN-gamma) was lower in the patients than in healthy volunteers (p < 0.05), and inversely correlated with the disease extent (p < 0.01). Tuberculous PPD-stimulated IFN-gamma as a percentage of PHA response (tuberculous PPD-IFN-gamma/PHA-IFN-gamma) was higher in the patients than in healthy volunteers (p < 0.05). However, tuberculous PPD-IFN-gamma/PHA-IFN-gamma did not correlate with the disease extent. Our results indicate that the tuberculous PPD-IFN-gamma/PHA-IFN-gamma may be useful for the diagnosis of tuberculosis but not for evaluating the disease severity, and suggest that PHA-IFN-gamma could be considered as a marker of disease severity.     

Immunological responsiveness of tuberculosis patients receiving rifampin

Rifampin has been shown to impair both humoral and cell-mediated immune responses in animal models. In order to detect a similar effect in man, 11 patients with active tuberculosis were evaluated before, 2 weeks after, and 12 to 16 weeks after initiating rifampin. Several parameters were serially measured including blood lymphocytes, intradermal response to intermediate strength tuberculin (PPD), and in vitro proliferative responses to phytohemagglutinin (PHA), a nonspecific mitogen, and to the specific antigens, PPD and influenza A. No changes in lymphocyte counts were noted. No changes in response were noted 2 weeks after beginning treatment with rifampin. However, compared with initial and 2-week responses, the PHA response was reduced by 47%, the PPD by 68%, and the influenza by 75%, and 6 of 11 patients showed no induration after tuberculin skin testing at the 12- to 16-week point. These results indicate that in doses employed for the treatment of tuberculosis, rifampin has an immunosuppressive effect in man that develops gradually.     

Expression of functional interleukin 2 receptors by peripheral blood monocytes from patients with active pulmonary tuberculosis.

Peripheral blood monocytes from patients with active tuberculosis are "activated" by a number of criteria, including selective depression of T-lymphocyte responses to the mycobacterial antigen, tuberculin-purified protein derivative (PPD). We studied monocytes from patients with tuberculosis and healthy skin test reactive controls for expression and function of IL 2 receptors (IL 2R). Depletion of adherent monocytes increased the IL 2 activity of supernatants of PPD-stimulated T cell cultures from patients by 30-fold. When cultured with purified IL 2, adherent cells from the patients depleted IL 2 activity by 66%. Monocytes from patients displayed IL 2R on their surface as evidenced by anti-Tac reactivity, and released soluble IL 2R into the medium during culture. The release of soluble IL 2R was augmented when monocytes were cultured with PPD. Finally, freshly isolated adherent monocytes from patients but not healthy individuals expressed the gene encoding Tac protein. Thus, blood monocytes from patients with tuberculosis express functional IL 2R constitutively. This property may be important in the immunoregulatory and effector function of mononuclear phagocytes during tuberculosis.     

T-lymphocyte differentiation in vitro in severe combined immunodeficiency. Defects of stem cells.

A study of T-lymphocyte differentiation was made on fractionated bone marrow cells from normal volunteers and from 11 patients with severe combined immunodeficiency (SCID) using normal thymic epithelial monolayers and their culture supernates as inducing agents. Normal marrow cells could regularly be induced to bear the human T-lymphocyte antigen (HTLA), to form rosettes with sheep erythrocytes (E rosettes), and to respond to the mitogen concanavalin A (Con A) after coculture with the thymic epithelial monolayers or their culture supernates. In contrast, studies of T-cell differentiation on the marrow cells of patients with SCID revealed varying defects, ranging from a complete "absence" of definable T-cell precursors to partial differentiation resulting in acquisition of one (HTLA) or two (HTLA and E rosettes) markers for T lymphocytes. Only in one patient was there induction of all three T-cell markers, namely, HTLA, E rosettes, and responsiveness to Con A. These observations indicate that SCID is a heterogeneous disorder in which defects of differentiation can occur at one or more multiple sites of differentiation leading the the clinical expression of T- and B-cell dysfunction. Further, our studies indicate that in T-cell differentiation, HTLA probably appears before the capacity to form E-rosettes, and development of the latter capacity is followed by a state of responsiveness to mitogens. A scheme of normal differentiation along with the defects of precursor T cells seen in SCID is presented.     

Cytochalasin B is a potent mitogen for chronic lymphocytic leukemia cells in vitro.

It is widely accepted that the neoplastic B cells from patients with chronic lymphocytic leukemia (CLL) respond poorly to common mitogens. The fungal metabolite cytochalasin B (0.5 micrograms/ml) is a weak mitogen for normal lymphocytes. However, when peripheral blood lymphocytes from 19 patients with CLL of B cell origin (B-CLL) were cultured with 0.5 micrograms cytochalasin B/ml, significant new DNA synthesis ( [14C]thymidine incorporation) occurred in 18. Stimulation indices with cytochalasin B varied widely (range = 1.9-28.2, mean +/- SD = 10.6 +/- 7.5; delta cpm range = 1,157-153,818; n = 26) but in 11 cases exceeded those seen with concanavalin A (Con A), phytohemagglutinin, or pokeweed mitogen. In all 11, the mitogenic response to cytochalasin B exceeded that to pokeweed mitogen, which is believed to be a T cell-dependent B cell mitogen. In three cases, the responses to cytochalasin B were 8.6, 3.5, and 2.3 times greater than those to Con A. As with other mitogens, the DNA synthetic response to cytochalasin B was time and dose dependent. Peak thymidine incorporation occurred at 72-88 h and declined thereafter. Significant mitogenic effects were observed with 0.1-5 micrograms cytochalasin B/ml with a peak at 0.5-2 micrograms/ml. Stimulated DNA synthesis was abolished by 1 mM hydroxyurea. Cells from two patients with B-CLL were separated by rosetting with sheep erythrocytes (E). Depletion of E-rosette-positive cells from the CLL cell population abolished the response to Con A but did not affect the response to cytochalasin B. Cytochalasin B is a potent mitogen for B-CLL cells and may be useful in cytogenetic studies of this often indolent neoplasm.     

Decreased T lymphocyte migration in patients with malignancy mediated by a suppressor cell population.

The migration and concentration of lymphocytes at sites of antigenic challenge are an integral part of the expression of delayed cutaneous hypersensitivity, as well as of tumor and graft rejection. In this study, we have analyzed the migration of T lymphocytes from patients with malignancy. We used casein and concanavalin A (Con A)-stimulated mononuclear cell supernatants to stimulate T cell locomotion. Peripheral blood T lymphocytes from 30 patients with established malignancy, 10 patients with indolent malignancy or benign tumor, and 42 normal adult controls were tested. Data are expressed as a migration index (MI), which represents the difference in micrometers between the distance migrated in response to a stimulus and the distance migrated in response to media alone. We observed a marked depression in casein-stimulated T lymphocyte migration in patients with established malignancy (mean MI +/- 1 SD = 17.0 +/- 9 microns) as compared with normal adult controls (mean MI +/- 1 SD = 35.3 +/- 10 microns). Similar results were observed with migration in response to Con A supernatants. T cells from patients with established malignancy had a mean MI of 5.8 +/- 4 microns to Con A supernatants as compared with 24.5 +/- 5 for controls. This depressed migration was apparent both in the distance that cells migrated and in the number of cells that migrated into the membrane. Of 10 patients with indolent malignancy or benign tumor, T cell migration in 8 was not significantly decreased as compared with controls. When we mixed equal concentrations of normal control T lymphocytes with T lymphocytes from patients with cancer and added the mixture directly to the upper compartment of the chemotaxis chamber, the response of the normal T cells to casein was inhibited by an average of 48%. We observed inhibition of this migration of normal cells when we added as little as 10% of patient cells to normal cells. When we mixed normal control T lymphocytes from different donors and added them directly to the upper compartment of the chemotaxis chamber, T lymphocyte migration in response to casein was not significantly altered. If T cells from patients with cancer were cultured overnight, the suppressive effect on lymphocyte locomotion was lost. Our results indicate that there is a population of T lymphocytes in patients with cancer that suppress normal T lymphocyte migration. This suppressor activity may partially explain the subversion of immunosurveillance in established neoplastic states, as well as the defective inflammatory reaction to intradermal injection of antigen observed in many patients with malignancy.     

Genetic control of lymphocyte activation: lack of response to low doses of concanavalin A in lipopolysaccharide-nonresponder mice

C3H/HeJ mice do not respond to the polyclonal B-cell activator lipopolysaccharide (LPS) from Escherichia coli; this was first described by Sultzer who observed that mice of this strain did not respond to an intraperitoneal (i.p.) injection of LPS as measured by the accumulation of leukocytes in the peritoneal cavity. Neither were C3H/HeJ mice as susceptible to LPS toxcitiy (1). It was later reported that LPS-induced mitogenesis (2,3), adjuvanticity (4), and the appearance of Ia antigens on B lymphocytes as induced by LPS, (5) was also absent in C3H/HeJ mice. However, lymphocytes from these mice respond normally to the polyclonal B-cell activators purified protein derivative of tuberculin (2,6) and dextran sulfate and have also been reported to respond normally to concanavalin A (Con A) (2). Furthermore, the immune responses to sheep erythrocytes (7) and soluble thymus-dependent antigens (4) are normal in C3H/HeJ mice. Unresponsiveness to LPS in C3H/HeJ mice has been found to Be due to a defect in a single gene or a set of linked genes (3,8) which has been mapped between the major urinary protein locus and the locus coding for polysyndactyly on chromosome 4. (1) We have reported that injection of LPS into mice of an LPS-responsive strain causes a shift in the Con A dose-response curve of cultured spleen cells, suppressing the low does response (9). Therefore, we tested the Con A proliferative response in cultures of normal or LPS-activated spleen cells from LPS-responder (C3H/Tif) and LPS-nonresponder (C3H/HeJ) mice. We report here that C3H/HeJ spleen cells respond poorly to low concentrations of Con A (0.05-0.1 μg/ml). Injection of LPS 2 days before culture inhibits the response to low doses of Con A in cultures of C3H/Tif spleen cells but has no inhibitory effect on the dose response profile of C3H/HeJ spleen cells. Furthermore, the low dose Con A response of spleen cells is dependent upon the presence of an Ia-positive cell. (2) The role of Ia-positive cells in the Con A response of C3H/Tif and C3H/HeJ spleen cells is described.     

Increased systemic T-lymphocyte reactivity in patients with established stroke.

We have analyzed the impact of stroke with subsequent hemiparesis and sensory loss on systemic in vivo and in vitro mediated immune functions. Delayed-type hypersensitivity (DTH) reaction to purified protein derivate (PPD, tuberculin), evaluated on the non-paretic side, was used as an in vivo measure of systemic antigen specific T-cell reactivity. Subcutaneous immunization with influenza vaccine was employed to analyse T-cell dependent B-cell function. The influence of stroke on T-cell function in vitro was studied by proliferative responses to PPD and Concanavalin A. Twenty five out of 54 (46%) stroke patients tested displayed positive DTH reaction to PPD. In contrast, only 24% of age matched controls displayed positive DTH reaction (p < 0.05). There was a good correlation between in vivo and in vitro reactivity to PPD. Consequently, peripheral blood mononuclear cells in 50% of stroke patients but only in 20% of matched controls showed proliferative response in vitro to PPD. Immunization of stroke patients and controls with influenza vaccine, a T-cell dependent B-cell antigen, raised equal antigen-specific serum IgG, IgA and IgM antibody responses in both study groups. We conclude that (a) stroke enhances systemic antigen-specific T-cell reactivity in vivo and in vitro, and (b) stroke has no significant effect on antigen-specific B-cell responses.     

PASSIVE TRANSFER OF TUBERCULIN SENSITIVITY BY TRITIATED THYMIDINE-LABELED LYMPHOID CELLS

Passive transfer of tritiated thymidine-labeled BCG sensitized lymphoid cells into homologous guinea pigs resulted in positive tuberculin skin reactions 24 hours after testing with PPD. Labeled cells were found specifically attracted to these sites. Labeled non-sensitized lymphoid cells did not appear at PPD injection sites, nor did labeled sensitized cells accumulate in non-specific inflammatory lesions. The specifically reacting tritiated cells were small, medium, and large lymphocytes and stem or immature cells of the lymphoid series. In the homologous system employed, positive skin tests were either minimal or absent 3 days after transfusion of activated cells. The injected labeled sensitized cells were rapidly cleared from the circulating blood and lodged in the lungs, spleen, and lymph nodes. Upon application of specific antigen they reappeared at the skin test site at 6 hours and then increased in number for the next 18 hours.     

Effects of cytotoxic immunosuppressants on tuberculin-sensitive lymphocytes in guinea pigs.

The immunosuppressive activities of two phase-specific drugs, 6-mercaptopurine (6-MP) and methotrexate, and a cycle-specific agent, cyclophosphamide, were evaluated on the lymphocytic component of established tuberculin hypersensitivity in guinea pigs. In these animals, purified protein derivative (PPD)-sensitive lymphocytes are in an intermitotic phase of their proliferative cycle. Neither phase-specific drug significantly altered either the number or functional activities of these lymphocytes. By two in vitro criteria, PPD-induced lymphoproliferation and elaboration of migration inhibition factor (MIF), the responses of lymph node cells were equivalent to sensitized controls. In addition, these agents did not deplete pools of T lymphocytes, impair responses to phytohemagglutinin (PHA), nor inhibit cutaneous reactivity if employed before sensitization. In contrast, cyclophosphamide showed broader immunosuppressive effects including significant toxicities for intermitotic lymphocytes. This drug depleted pools of T cells and markedly impaired the in vitro proliferative responses of residual lymphocytes. The latter occurred with both PHA and PPD. Suppression of PHA reactivity was a dose-dependent phenomenon but was evident even with small quantities of this alkylating agent. The suppression of antigen-induced responses was independent of the proliferative status of target lymphocytes in vivo, after a single large dose, it persisted for more than 3 wk. In total, these results indicate that the effective use of cytotoxic drugs as immunosuppressants must include consideration of both the cycle specificities of the agent and the proliferative activities of the target lymphoid population.     

Specific antibodies to different mycobacterial antigens in patients with pulmonary tuberculosis]

Antibodies to three mycobacterial antigens, Soviet tuberculin and ultrasound-treated Mycobacterium tuberculosis (H37Rv) and M. bovis (BCG) were detected by enzyme immunoassay in 90 patients with pulmonary tuberculosis and 75 normal subjects. Antibody detection rates and levels were found related to the form of tuberculous process. The detection rate was rather low in focal tuberculosis and virtually the same for all the antigens (15.3 percent). In disseminated processes (infiltrative and particularly disseminated and fibrous-cavernous) antibodies are detected more often in higher titers than in local processes, and their levels are different with different antigens. The method was more sensitive with ultrasound-treated antigens of M. tuberculosis (H37RV) and M. bovis (BCG) than with PPD. Simultaneous enzyme immunoassay with three antigens detected up to 75 percent of antituberculous antibodies in infiltrative, up to 92 percent of antibodies in disseminated, and up to 100 percent of antibodies in fibrous-cavernous tuberculosis.     

脑脊液单核细胞内结核抗原检测在结核性脑膜炎早期诊断中的价值

目的探讨脑脊液单核细胞内结核抗原检测在结核性脑膜炎临床诊断中的价值。方法脑脊液样本120例,其中结核性脑膜炎组60例,对照组60例,采用免疫组化法检测脑脊液中单核细胞内的结核抗原,同时进行脑脊液细胞学检查。结果与对照组比较,结脑组中性粒细胞、淋巴样细胞(包括转移淋巴)、激活单核细胞明显升高,差异均有统计学意义(χ2分别=22.76、17.05、4.04、11.76,P均<0.05)。结核性脑膜炎患者脑脊液中单核细胞内存在结核菌素抗原,60例结核性脑膜炎患者中首次检查48例阳性,敏感性为80.00%;对照组有1例阳性,特异性为98.33%,结核性脑膜炎组和对照组多次检测结果敏感性和特异性均较高,差异均有统计学意义(χ2分别=76.19、71.55、35.28,P均<0.05)。结论检测脑脊液中单核细胞内结核抗原可以做为结核性脑膜炎早期诊断的一种重要手段。     

Antigen responsiveness during tuberculosis: regulatory interactions of T cell subpopulations and adherent cells

Previous studies from this laboratory demonstrated that adherent mononuclear cells selectively decreased in vitro tuberculin responses in some anergic patients with tuberculosis; subsequently this adherent suppressor cell was characterized as a monocyte. The current study of 41 patients with active pulmonary tuberculosis examined whether T cell subpopulations also acquired antigen-specific suppressor function during Mycobacterium tuberculosis infection, contributed to monocyte-mediated suppression of tuberculin responses, or both. Alteration in the numbers of circulating T-helper (Leu 3a) and T-suppressor (Leu 2a) cells was not observed in patients with tuberculosis, nor did Leu 2a cells selectively modulate in vitro tuberculin responses. The numbers of circulating T gamma cells, a subset of T cells identified by surface receptors for the Fc portion of IgG (Fc gamma R), was increased twofold in patients with active pulmonary tuberculosis. Depletion of T gamma cells from in vitro cell culture consistently and selectively increased tuberculin responsiveness of T cells from patients with tuberculosis. In addition, in the absence of T gamma cells, monocyte-mediated suppression of tuberculin responses was demonstrated in each patient observed. These studies demonstrate that during M. tuberculosis infection T gamma cells acquire antigen-specific suppressor cell activity and suggest that T gamma cells also contribution to immunoregulation modulating the expression of tuberculin-specific suppression by monocytes.     

Study of IgG antibodies to PPD with an immunoenzyme method (ELISA) in the serum of patients with pulmonary tuberculosis

ELISA has been used for the detection of IgG antibodies against PPD in 48 patients with pulmonary tuberculosis, in 10 individuals with previously treated tuberculosis and clinically recovered, in 22 PPD skin-test positive healthy volunteers and in 48 blood donors with unknown PPD skin-test. Positivity was obtained in 29 patients (83%) with active tuberculosis, in one patient (10%) with clinical recovery, in none of the healthy controls. This technique may have a potential diagnostic relevance in evaluating patients with suspected pulmonary tuberculosis.