Use of intravenous immune globulin in patients receiving bone marrow transplants

Risk of infection according to the gamma globulin level in the 100 days following allogeneic stem cell transplantations

BACKGROUND

Immunoglobulin replacement therapy is recommended in case of severe hypogammaglobulinemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the supposed increased risk of infection in case of hypogammaglobulinemia has not been confirmed in allo-HSCT. In this study, we assessed the relationship between the gamma globulin level and the risk of infection during the 100 days following the allo-HSCT.

METHODS

We gathered the weekly laboratory tests from day 7 to day 100 of 76 allograft patients, giving a total of 1 044 tests. 130 infections were documented clinically, by imaging, or microbiologically.

RESULTS

Average gamma globulin levels between D-7 and D100 did not differ between patients with or without infection (642 ± 232 and 671 ± 246 mg/dL, respectively, P = .65). Gamma globulin level <400 mg/dl was not associated with the occurrence of infection between the test studied and the next one (aOR 1.33 [0.84-2.15], P = .24). The gamma globulin level was not predictive of bacterial or fungal infections (AUC 0.54 [95%CI: 0.47-0.61]) nor of viral reactivations (AUC 0.51 [95%CI: 0.43-0.60]).

CONCLUSIONS

This confirmed that the humoral deficiency is a minor part of the immune deficiency in the 100 days post-transplant. This questions the relevance of the indications of immunoglobulin substitution during this period.

B in TB: B Cells as Mediators of Clinically Relevant Immune Responses in Tuberculosis

The protective role of B cells and humoral immune responses in tuberculosis infection has been regarded as inferior to cellular immunity directed to the intracellular pathogen Mycobacterium tuberculosis. However, B-cell–mediated immune responses in tuberculosis have recently been revisited in the context of B-cell physiology and antigen presentation. We discuss in this review the diverse functions of B cells in tuberculosis, with a focus on their biological and clinical relevance to progression of active disease. We also present the peptide microarray platform as a promising strategy to discover unknown antigenic targets of M. tuberculosis that could contribute to the better understanding of epitope focus of the humoral immune system against M. tuberculosis.

The role of intravenous immunoglobulin in treatment of mucous membrane pemphigoid: A review of literature

BACKGROUND

Mucous membrane pemphigoid (MMP) is considered an autoimmune blistering disease that predominantly affects mucous membranes. Various treatments are available for controlling the diseases, but not all of them may respond.

MATERIALS AND METHODS

PubMed and Google Scholar were searched for all the associated studies until 2015, using the keywords such as "cicatricial pemphigoid" or "ocular pemphigoid" or "mucous membrane pemphigoid" or "MMP" and "intravenous immunoglobulin" or "IVIg" to find all the relevant studies. The last search update was for September 2, 2015. Among the searched items, only English studies were included in the review.

RESULTS

After excluding nonrelevant studies, 13 studies with a total number of seventy patients with MMP who were under treatment with IVIg were analyzed. The 65 patients responded completely, one did not respond, two had partially responded, and the remaining two patients stopped IVIg therapy, which resulted in ocular cicatricial pemphigoid progression. Majority of the studies reported mild adverse effects while two of them did not report any unwanted side effect. The most common side effect was headache, followed by nausea. Most of the patients who had a cessation of IVIg therapy before achieving clinical remission experienced the disease progression.

CONCLUSION

Overall, it can be concluded that IVIg therapy was very helpful in treatment of MMP patients who did not respond to conventional therapy or stopped using them for various side effects. Adverse effects associated with IVIg therapy were considerably lower than conventional therapy that can lead toward treatment with this agent in patients who suffer from severe side effects.

The history and evolution of immunoglobulin products and their clinical indications

The history of providing antibodies to treat diseases began in the 19th century with the discovery of tetanus and diphtheria toxins and the demonstration that immunity to tetanus and diphtheria infections could be transferred by immune sera. Characterization of the mediators of this immunity resulted in the discovery that antibodies are proteins that can be isolated and used to protect against infectious diseases. Development of a method to isolate antibodies from human plasma that could be safely injected into people initiated the development of human gamma globulin preparations to provide antibodies to patients with inherited antibody deficiencies. To overcome the limitations imposed by intramuscular injection of gamma globulin, intravenous gamma globulin preparations were developed that began to be used in a wide variety of clinical conditions. Thus the original clinical indication for infection prevention was expanded to several other indications that employ large doses to suppress inflammatory and autoimmune disorders. The most recent development in immunoglobulin therapy is the production of concentrated immune globulins for subcutaneous injection. Home infusions of subcutaneous immunoglobulin are increasingly used to treat immunodeficient patients and are being studied for other clinical applications.

Intravenous immunoglobulins: evolution of commercial IVIG preparations

Since its first use in 1952, human immunoglobulin has been used to treat people who have inherited antibody deficiencies. This article summarizes IVIG clinical development in primary immunodeficient patients and manufacturing improvements introduced over time. Manufacturing improvements include purification procedures that have reduced the incidence of adverse events and improved clinical efficacy, as well as virus inactivation and removal steps that have increased safety from blood-borne infections. Current manufacturing procedures, IVIG production trends, and recent clinical trial results are also reviewed.

Properties of a new intravenous immunoglobulin (IGIV-C, 10%) produced by virus inactivation with caprylate and column chromatography

BACKGROUND AND OBJECTIVES

Current manufacture of intravenous immunoglobulin (Gamimune N) uses four cold-ethanol precipitation steps and solvent-detergent treatment. Our objective was to design a new manufacturing process to maximize immunoglobulin G (IgG) purity, achieve robust viral safety, preserve all the biological activities of antibody and avoid unnecessary protein loss.

MATERIALS AND METHODS

The new process combines multiple functions in single steps. Caprylate is added to precipitate non-IgG proteins and to inactivate enveloped viruses. Two successive anion-exchange columns are used to purify IgG and remove caprylate. The new product, IGIV-C (Gamunex, 10%) is formulated with glycine at 100 mg/ml IgG, pH 4.25. Vials are incubated for 21 days at 23-27 degrees C in a final virus-inactivation step.

RESULTS

Compared with the process for production of Gamimune N, that for IGIV-C requires a shorter production time, achieves more robust virus inactivation, increases IGIV yield from plasma, improves physiological IgG subclass distribution (resulting in higher levels of IgG4), and improves purity, with lower levels of IgA (40 microg/ml), IgM (< 2 microg/ml) and albumin (< 20 microg/ml). Antibody binding, opsonization and protective activities are similar.

CONCLUSIONS

Compared with the current commercial process, the new IGIV-C manufacturing process produces a more highly purified preparation that contains slightly higher levels of IgG4 and retains antibody activities required for clinical efficacy.

Pharmacokinetics of an anti-cytomegalovirus hyperimmunoglobulin after single intravenous administration to healthy volunteers

By selecting blood donors with high cytomegalovirus (CMV) antibody titres, a plasma pool was obtained which was used to produce an IgG hyperimmunoglobulin by means of pepsin fractionation. After administration of approximately 100 mg/kg body weight to healthy subjects, the time course both of anti-CMV IgG antibody titres by ELISA and of virus neutralisation (VN) titres was followed for 15 days. Seronegative subjects showed an increase in CMV-IgG antibodies as well as a significant enhancement of VN. The time course of both titres was non-uniform. The decline of both titres was biphasic: CMV-IgG antibodies fell slowly during the first week and remained unchanged thereafter, whereas VN titres decreased markedly faster in the first than in the second week. In seropositive subjects, on the other hand, VN remained unchanged. CMV-IgG antibodies increased by approximately 3 times, followed by a similar biphasic decline as seen in seronegative subjects. Due to the differences between seronegative and seropositive subjects and to the non-uniform time course, no calculations of the elimination rate were feasible.

Detection by enzyme-linked immunosorbent assay of specific immunoglobulin G isotypes in primary and established cytomegalovirus infections

An enzyme-linked immunosorbent assay using monoclonal antibodies was developed to study the subclass distribution of immunoglobulin G (IgG) to cytomegalovirus (CMV) in individuals from a number of clinical groups. Most CMV-seropositive individuals had IgG1 and IgG3. IgG2 and IgG4 were detected less frequently at very low levels of activity, mostly among mothers at delivery and renal patients. Most seroconversions were accompanied by an important increase of the IgG1 activity, whereas IgG3 appeared at lower levels; neither IgG2 nor IgG4 occurred. This suggests that these isotypes play a secondary role in the response to the CMV infection and that they may be considered markers of past infections. Anti-CMV IgG1 is the most efficiently transmitted through the placenta. Whether infected or not, newborns had the same subclass distribution and activity levels as their mothers. Isotype determination did not offer a decisive explanation of a number of discrepancies observed between CMV IgG enzyme-linked immunosorbent assay and complement fixation test results.

Lymphocyte phenotypes in the abomasal mucosa of sheep infected with Haemonchus contortus

Lymphocyte subpopulations in the abomasal mucosa of worm-free and parasitized sheep were assessed in situ. A preponderance of T-lymphocytes, with approximately equal numbers of cells expressing CD5, CD4 and CD8 antigens, was found. Most of the lymphocytes expressing CD8 lacked CD5. Using a panel of 15 monoclonal antibodies to ovine leucocyte antigens, abomasal lymphoid follicles in the mucosa were shown to resemble lymph node follicles phenotypically. Abomasal epithelial cells contained major histocompatibility complex (MHC) class II antigen. Infection or hyperimmunization of pasture-reared sheep with the gastric nematode Haemonchus contortus increased the numbers of mucosal mast cells and eosinophils but did not alter the phenotypic composition or number of mucosal lymphocytes or the pattern of expression of MHC class II antigens.

Drug-induced skin reactions and acute cutaneous graft-versus-host reaction: a comparative immunohistochemical study

Skin biopsies from eight patients with drug-induced dermatitis have been compared with skin biopsies from 16 patients developing skin lesions (acute graft versus host-reaction and/or drug-induced reaction) after bone marrow transplantation. Biopsies were investigated using immunohistochemistry and several monoclonal antibodies. Morphological and immunohistochemical patterns in skin biopsies of both groups were very similar. The only difference seen was a reduced number of epidermal Langerhans cells with poorly developed dendrites in skin biopsies taken from patients who underwent bone marrow transplantation. If the latter finding is due to the cytotoxic drug regimen administered before bone marrow transplantation, as previously stated, we doubt the usefulness of skin biopsies in the differential diagnosis of acute graft-versus-host reaction and drug-induced skin lesions.

Corticosteroids for prevention of adverse reactions to intravenous immune serum globulin infusions in hypogammaglobulinemic patients

Severe adverse reactions to intravenous immune serum globulin occurred repeatedly in four of 10 hypogammaglobulinemic patients. Treatment-limiting symptoms included fever, chills, headache, hypertension, and chest pain. Pretreatment of patients with hydrocortisone immediately prior to infusion prevented subsequent adverse reactions and permitted these patients to receive immune serum globulin intravenously.

Elimination of nonspecific cytomegalovirus immunoglobulin M activities in the enzyme-linked immunosorbent assay by using anti-human immunoglobulin G

Direct enzyme-linked immunosorbent assay methods offer several advantages in assessing past or recent exposure to cytomegalovirus (CMV) infection, but there persist many pitfalls in the use of these methods for determining specific immunoglobulin M (IgM). The efficiency of absorption of sera by IgG-coated latex beads, aggregated human IgG, or Staphylococcus aureus, i.e., for removing nonspecific CMV IgM activities, was evaluated in comparison with the effect of an anti-human IgG hyperimmune serum. Large routine series comprising serum samples from patients of various clinical groups and healthy individuals were examined. The CMV IgM-positive samples were at first treated with latex or aggregated IgG, but these absorptions left too many CMV IgM-positive individuals. S. aureus increased the nonspecific activity of some sera and, in other cases, removed or impaired specific IgM activities. The anti-IgG treatment caused the disappearance of nonspecific CMV IgM activities that had resisted the other treatments, whereas specific activities remained intact. Utilizing this method, only 1.03% of the routine series patients remained CMV IgM positive by the enzyme-linked immunosorbent assay, a figure in good agreement with a mean probability of CMV antibody acquisition of 0.33% for the population living in Belgium. On the other hand, in a series of patients who were investigated for serological response to several viruses, eight individuals displayed multiple IgM activities after anti-IgG treatment. In these cases, most IgM activities were found in patients who had IgG toward the related antigen for a long time before transient IgM was detected. This result implies that to assess a diagnosis of primary infection, it is necessary to examine serial specimens for IgG acquisition accompanying specific IgM.

Prevention and treatment of cytomegalovirus infections with interferons and immune globulins

With the exception of congenitally-infected infants, cytomegalovirus infection is generally benign in persons with normal host defenses. In contrast, among immunosuppressed patients, these infections may be severe and sometimes fatal. Treatment of cytomegalovirus infection with presently available antiviral agents including interferons has not been successful. Prevention of infection has been successful in several circumstances, however. Cytomegalovirus is transmitted by blood products from seropositive donors, and screening to remove seropositive blood products or freezing to destroy leukocytes has been effective amont neonates, cardiac transplant patients and renal dialysis patients. An alternative approach used among marrow transplant patients is passive immunization of seronegative patients with plasma or globulins with high antibody titers against cytomegalovirus. Alpha interferon given prophylactically has been effective in delaying virus reactivation and reducing the severity of infection among seropositive renal transplant patients. All of these approaches, as well as the continued development of more effective antiviral agents, will be needed for control of cytomegalovirus infection.

Intravenous immune globulin for hypogammaglobulinemia: a comparison of opsonizing capacity in recipient sera

Twelve severely hypogammaglobulinemic patients received infusions of alkylated immune globulin and two other native nonalkylated products. Administration was separated by an interval of 3 weeks. Serum was obtained prior to and at 24 hr and 3 weeks after each infusion for measurement of total IgG, specific and opsonizing antibodies. The latter was accomplished against Streptococcus pneumoniae types 5, 12F and 14 and zymosan using chemiluminescence methodology. Changes in total IgG concentrations were comparable for the three products. Prior to enrollment, IgG levels averaged 115 +/- 72 mg/dl, increasing to 779 +/- 399 at 24 hr postinfusion, and were 337 +/- 200 after 3 weeks. No differences among the products were seen in their ability to produce antibodies against Herpes simplex virus types 1 and 2, rubella, toxoplasma, cytomegalovirus, or tetanus. However, differences in opsonizing antibody were observed between alkylated and native IgG preparations. Peak chemiluminescence responses of neutrophils following opsonization of S. pneumoniae with native immune globulin were significantly higher than with alkylated IgG, indicating greater functional capacity. These studies suggest that native immune serum globulin provides a greater potential for augmenting host defense mechanisms against pneumococcal infection in hypogammaglobulinemic patients.

Flow cytometry of leukocytes after intravenous fluorescein angiography

Blood specimens were obtained for T lymphocyte analysis from patients undergoing intravenous fluorescein angiography (IVFA). Mononuclear cells were prepared by differential density centrifugation and analyzed by flow cytometry (FCM). Prior to IVFA, there was very little autofluorescence in the mononuclear cell population. After IVFA, there was an increase in the fluorescence of the mononuclear cells. Though barely visible by fluorescence microscopy, the fluorescence was uniformly distributed throughout the cytoplasm. By FCM, fluorescein was detected in 27% of the lymphocytes, 61% of the monocytes, and 75% of the granulocytes. Care must be taken when interpreting flow-cytometric lymphocyte subset data because of the increased nonspecific fluorescence of mononuclear cells in patients who have undergone IVFA.

Immunohistological skin alterations in allogeneic bone marrow transplantation

Skin biopsies of 26 patients with leukemia and seven patients with aplastic anemia were investigated before and at different stages after allogeneic bone marrow transplantation (BMT) to establish the immunological criteria which distinguish skin alterations during normal reconstitution from dermal lesions mediated by graft-versus-host disease (GvHD). Of the 33 patients studied 27 presented with clinically diagnosed acute and/or chronic GvHD, one patient died of bone marrow rejection. Immunohistological analysis of the respective skin biopsies with selected monoclonal antibodies against human leukocyte antigens (HLA) and differentiation antigens of the lympho-hematopoietic cells revealed low dermal mononuclear cell counts with phenotypically normal constituents in five cases with uncomplicated reconstitution post-grafting. In contrast, increased dermal cellular infiltrates predominantly consisting of Lyt 3+, OKT 8+ T-lymphocytes, as well as of a large number of Ia-like (immune response associated = HLA-D) determinant + monocytes/macrophages were observed in all patients with active acute/chronic GvH reactivity. As sign of activation simultaneous expression of HLA-D region products was also found on a subset of the invading OKT8+ T-lymphocytes. Progression of GvHD was associated with additional surface staining of keratinocytes for Ia-like determinants. Loss of Ia-like determinant+, OKT6+ dentritic epithelial cells in all leukemic patients, as well as in patients with aplastic anemia with or without GvHD suggested damage of Langerhans cells due to the previous radiotherapy and/or specific immunological destruction. In patients with fatal outcome of GvHD prolonged reduction of these dentritic epithelial cells seemed to be indicative of impaired immune reconstitution or bone marrow dysfunction. Thus immunopathological features of skin GvHR may enable early recognition and prognostic evaluation of this disease possibly allowing more effective therapy.

Comparative anti-Pseudomonas aeruginosa activity of chemically modified and native immunoglobulin G (human), and potentiation of antibiotic protection against Pseudomonas aeruginosa and group B Streptococcus in vivo

Immunoglobulin G intravenous is prepared by controlled reduction and alkylation of approximately four interheavy chain disulfide bonds per molecule. To determine if the protective activity of antibody modified by this process is diminished, mice were treated with identical doses of reduced and alkylated IgG and native IgG prepared from the same plasma pool. Three hours later mice were given a 10 percent body surface burn followed by challenge with the seven Fisher-Devlin-Gnabasik immunotypes of Pseudomonas aeruginosa. Against five of the seven immunotypes, the 50 percent protective doses were approximately 100 mg or less per kg body weight. Overall there was no significant difference in protection afforded to the mice by the two immunoglobulin preparations indicating that in vivo the activity of IgG against P. aeruginosa remains unimpaired by reduction and alkylation. In the second part of this study, immunoglobulin G intravenous significantly enhanced the activity of tobramycin and carbenicillin in the treatment of P. aeruginosa infection in burned mice and of penicillin G in the treatment of group B Streptococcus 1C infection in normal mice.

Replacement therapy with modified immunoglobulin G in burn patients: preliminary kinetic studies

Suppression of serum immunoglobulin G for periods ranging from days to weeks following thermal injury may enhance the risk of infection in burn patients. In an initial trial, we attempted to determine whether intravenous pulses of Immunoglobulin G (IgG) will establish and maintain normal serum IgG concentrations in this interval. The levels of endogeneous serum IgG in eight control patients, mean total burn size 45 percent body surface area (no IgG infusions), were measured by radial immunodiffusion on various postburn days. Commercially available reduced alkylated IgG (5 percent Gamimune, Cutter Biological, Berkeley, California) was infused in doses of 500 mg/kg twice per week in four patients (total burn size 32 percent) and once per week in five patients (total burn size 47 percent), beginning during the first postburn week. Circulating IgG was measured prior to each infusion and at three postinfusion times: (1) 15 minutes (peak), (2) one day, and (3) either day 3, 4, or 6. Surgery or blood transfusions prior to one of these time points invalidated kinetic analysis of some infusions. Exponential two-point decay constants for total serum IgG after each of 24 infusions were calculated separately for early (day 0-1) and later (day 1-3 or 1-4) postinfusion intervals and assessed by stepwise regression analysis to determine sources of variation in decay. Early decay was seen to be faster with larger burn size after accounting for variation of decay with preinfusion and peak IgG values. Later decay was not related to burn size. Maltose, a constituent of the IgG preparation, was detectable in serum for only four to eight hours after each infusion and may have contributed to a 20 percent increase in total serum glucose between four and eight hours postinfusion. Mean serum IgG in patients given infusions twice weekly was in the normal range after one infusion, about a week earlier than in untreated patients. Such infusions maintained normal IgG levels.

Protective activity of an intravenous immune globulin (human) enriched in antibody against lipopolysaccharide antigens of Pseudomonas aeruginosa

Human plasmas containing naturally high levels of immunoglobulin G (IgG) to lipopolysaccharide antigens of Pseudomonas aeruginosa immunotypes 1, 2, 4, and 6 were identified by an enzyme-linked immunosorbent assay. The high titered plasmas were collected, pooled, and fractionated. Cohn fraction II IgG was prepared for intravenous infusion. The antibody titers in the hyperimmune intravenous immunoglobulin preparation were approximately fivefold higher against P. aeruginosa immunotypes 1, 2, 4, 5, and 6 and approximately twofold higher against immunotypes 3 and 7 than conventional intravenous immunoglobulin G. When tested for prophylaxis in burned mice, the protective doses 50 percent of Pseudomonas-intravenous immunoglobulin G were approximately fourfold less effective against immunotypes 1, 2, 4, and 7 and International Antigenic Typing System Serotypes (IATS), 8 (= immunotype 6) than conventional intravenous immunoglobulin G. Against immunotype 3 and 5, IATS 13, 15, and 16, both immunoglobulin preparations afforded similar levels of protection. In burned mice challenged with immunotypes 1 and 2 and not treated until 18 hours after infection, Pseudomonas-intravenous immunoglobulin G and tobramycin had synergistic activity in preventing death. Pseudomonas-intravenous immunoglobulin G also afforded significant protection to immunosuppressed mice challenged with immunotype 1. These data suggest that Pseudomonas-intravenous immunoglobulin G may be useful in prevention or treatment of P. aeruginosa infections in man.

Intravenous immunoglobulin for modification of cytomegalovirus infections associated with bone marrow transplantation. Preliminary results of a controlled trial

The effects of immune globulin intravenous, 5 percent in 10 percent maltose, on cytomegalovirus infection and interstitial pneumonia in bone marrow transplants were evaluated in a randomized controlled trial. Eighteen patients were given weekly doses (20 cc/kg) of intravenous immunoglobulin before and after transplantation, and 18 patients were controls. The incidence of cytomegalovirus infection was similar in the control and intravenous immunoglobulin-treated groups, but symptomatic cytomegalovirus infection (eight of 18 versus three of 18, p = 0.14) and interstitial pneumonia (10 of 18 versus four of 18, p = 0.08) occurred less frequently in the group receiving intravenous immunoglobulin. Cytomegalovirus pneumonia developed in eight control patients and in three patients receiving intravenous immunoglobulin (p = 0.14), whereas two control patients and one patient receiving intravenous immunoglobulin experienced idiopathic interstitial pneumonia. These preliminary results suggest that intravenous immunoglobulin can modify the severity of cytomegalovirus infection and prevent interstitial pneumonia in bone marrow transplant recipients.

Prevention and treatment of cytomegalovirus infections with interferons and immune globulins

With the exception of congenitally-infected infants, cytomegalovirus infection is generally benign in persons with normal host defenses. In contrast, among immunosuppressed patients, these infections may be severe and sometimes fatal. Treatment of cytomegalovirus infection with presently available antiviral agents including interferons has not been successful. Prevention of infection has been successful in several circumstances, however. Cytomegalovirus is transmitted by blood products from seropositive donors, and screening to remove seropositive blood products or freezing to destroy leukocytes has been effective among neonates, cardiac transplant patients and renal dialysis patients. An alternative approach used among marrow transplant patients is passive immunization of seronegative patients with plasma or globulins with high antibody titers against cytomegalovirus. Alpha interferon given prophylactically has been effective in delaying virus reactivation and reducing the severity of infection among seropositive renal transplant patients. All of these approaches, as well as the continued development of more effective antiviral agents, will be needed for control of cytomegalovirus infection.

Immunohistological study in sarcoidosis: evaluation at different sites of disease activity

Sarcoidosis is a multisystem disease characterized by enhanced immune responses at sites of involvement. For this reason, an immunohistological study using monoclonal antibodies against T-cell subpopulations was carried out in order to evaluate the topographic distribution of immunocompetent cells in tissue sections obtained from a variety of involved organs, such as parenchymal lung, lymph nodes, eyes, skin, and liver. Biopsy specimens were also stained for detection of immunoglobulins, complement, and fibrinogen deposits. The data demonstrate a redistribution of T cells from the blood to all the sites of disease activity where they account for the large majority of infiltrating cells, both in the early lesions (merely a lymphocytic infiltrate) and in well-organized granulomas. Moreover, these cells express a helper-related phenotype, as demonstrated by the high Leu-3/Leu-2 ratios, at sites of involvement with respect to the blood (blood, 1.8/1; transbronchial lung biopsies, 10.5/1; lymph nodes, 19/1; skin, 28/1; liver, 22/1; eye, 14/1). In line with this helper infiltration is the presence of plasma cells and immunoglobulin deposits, suggesting a local hyperreactivity of the B-cell immune system. Both the hypergammaglobulinemia and the T lymphopenia usually observed in the blood of sarcoid patients could be explained by these observations. Comparative analysis of immunohistological data and bronchoalveolar lavage (BAL) findings provides further evidence that BAL cellularity reflects the changes already occurring in lung histology. The studies emphasize the importance that immunological phenomena play in the pathogenesis of sarcoidosis and provide new insights into the mechanisms leading to the formation and maintenance of the sarcoid granuloma.