Guidelines for clinical and laboratory evaluation patients with monoclonal gammopathies

This guideline provides the recommendations of an expert panel for the clinical and laboratory evaluation of patients suspected of having a clinical condition that produces a monoclonal protein in serum or urine. The recommendations describe the clinical conditions in which a monoclonal protein should be sought, the optimal sequence of testing to diagnose and monitor these patients, and the most effective laboratory procedures.

Procedures for the evaluation of monoclonal immunoglobulins

A wide variety of techniques are available for the screening, characterization, and quantification of monoclonal proteins. These techniques vary in regard to the expense, skill and intensity of labor involved, and sensitivity for detection of low levels of monoclonal proteins or of those with unusual migration. Detection of monoclonal proteins requires the use of high-resolution electrophoresis (either gel-based or capillary) and immunofixation (or immunosubtraction). Immunoelectrophoresis is not recommended. Urine for detection of monoclonal free light chains should be from 24-hour samples, and the aliquot should be concentrated at least 100-fold prior to electrophoresis and immunofixation. Dipstick and sulfosalicylic acid techniques are not sensitive enough to detect small quantities of monoclonal free light chains and should not be used as screening tests for this purpose.

The effects of exogenous free fatty acids on lipoprotein migration in serum high-resolution electrophoresis: addition of free fatty acids improves visualization of normal and abnormal alpha1-antitrypsin

Abnormalities in the alpha1 region are occasionally difficult to interpret on high-resolution electrophoresis (HRE) gels because alpha1-antitrypsin (A1AT) can be obscured by elevated levels of lipoprotein. The addition of saturated free fatty acids (SFFAs) to serum samples causes a selective anodal migration of lipoproteins when examined by HRE. This "clearing" of the alpha1 region improves visualization of A1AT. In this study, we evaluated 6- to 24-carbon SFFAs for their ability to cause anodal migration of serum lipoproteins; identified the optimal SFFA and determined its effects on other proteins; and applied the SFFA to problematic serum samples, including those containing dense alpha lipoprotein regions. When added to serum samples, a mixture of medium-chain (12-18 carbon) SFFAs caused a dose-dependent anodal migration of the alpha and beta lipoproteins and albumin. Lauric acid (C(12:0); 3.2-6.5 mmol/L) caused an optimal effect--maximal anodal migration of alpha lipoproteins and clearing of the alpha1 region, facilitating inspection of that area for A1AT variants. At the optimal C(12:0) concentration, the migration and resolution of A1AT were minimally affected, anodal slurring of beta lipoproteins and albumin were slight, and there was no effect on interpretation of monoclonal proteins. At higher concentrations, C(12:0) increased anodal migration of beta lipoproteins and decreased the resolution of A1AT. C(12:0) at 3.2 mmol/L in serum samples of heparinized patients showed an exaggerated effect similar to higher concentrations of C(12:0) in nonheparinized serum samples. Hyperbilirubinemia did not alter the effect of C(12:0) on serum proteins. C(12:0) treatment of serum samples displaying dense alpha lipoprotein bands on HRE dramatically improved visualization of A1AT. We report the incidental identification of A1AT variants in two such samples treated with C(12:0). The addition of C(12:0) to serum samples markedly improves visualization of normal and abnormal A1AT in the alpha1 region in HRE.

Autoimmune reactivity in inflammatory bowel disease

Inflammatory bowel disease remains a poorly understood chronic inflammatory condition of the bowel. No etiologic agents, or agreed upon pathogenesis is currently known. Recent findings that perinuclear antineutrophil cytoplasmic antibodies (P-ANCA) are present in the vast majority of patients with this disease have proven to be of use in epidemiologic studies. Its clinical use is currently being explored by several investigators.

Mucosal unresponsiveness to aflatoxin B1 is not broken by cholera toxin

Rabbits immunized via chronically isolated ileal loops with aflatoxin B1 (AFB) conjugated to porcine thyroglobulin (TG) mixed with the mucosal adjuvant cholera toxin (CT) produced very small mucosal antibody responses to AFB. Strong mucosal and systemic antibody responses to CT and TG were generated by this immunization protocol, suggesting that the observed unresponsiveness was specific to AFB. Parenteral immunization with AFB-TG produced strong serum IgG anti-AFB responses, indicating that the conjugate preparation was immunogenic and that the rabbits possess the requisite systemic B and T cell repertoires to recognize and respond to AFB. This mucosal unresponsiveness was distinct from oral tolerance, as animals immunized mucosally with AFB-TG mixed with CT produced vigorous serum IgG anti-AFB responses upon subsequent parenteral immunization with AFB-TG. In vitro mitogen stimulation of lymphocytes isolated from Peyer's patches and mesenteric lymph nodes of unimmunized rabbits revealed the presence of AFB-specific B cells at levels comparable with these found in the spleen. These observations indicate that unresponsiveness to AFB is hapten-specific, restricted to the mucosa, and refractory to the adjuvancy of CI.

Selective induction of mucosal immune responses to 2-acetylaminofluorene

Mucosal vaccination with chemical carcinogens coupled to enterotoxins such as cholera toxin (CT) can elicit carcinogen-specific immunoglobulin secretion into the intestinal lumen. The present study examines the ability of several related bacterial enterotoxins and their subunits to act as adjuvants or carrier proteins in stimulating an intestinal secretory IgA (S-IgA) response to 2-acetylaminofluorene (AAF). Using Thiry-Vella loops in rabbits, CT, cholera toxin B subunit (CTB) and the recombinant B subunit of the heat labile enterotoxin from E. coli (rLTB) were all found to be effective carrier proteins and adjuvants for eliciting S-IgA anti-AAF. However, marked differences in the ratio of mucosal S-IgA to serum IgG production were observed. CT elicited the highest luminal S-IgA anti-AAF titers as well as the highest ratio of intestinal S-IgA/serum IgG when used as an adjuvant. Conversely, rLTB elicited a high serum IgG anti-AAF titer but only a modest intestinal S-IgA response. Dialysis studies using monoclonal IgA versus IgG anti-AAF on opposing sides of a semipermeable membrane demonstrated the potential importance of the intestinal S-IgA/serum IgG ratio. A high "intestinal" IgA/"serum" IgG ratio abolished carcinogen transfer to the "serum" side of the membrane, while a low ratio enhanced transfer. Thus, to generate an active mucosal immune response capable of blocking carcinogen absorption, the carrier protein or adjuvant should be selected to optimize the intestinal S-IgA/serum IgG ratio.

Polymerase chain reaction-mediated site-directed mutagenesis detection of Z and S alpha-1-antitrypsin alleles in family members

Alpha-1-antitrypsin (A1AT) deficiency is an autosomal hereditary disorder with a reduction in serum A1AT levels. In a large family, we used a polymerase chain reaction (PCR)-mediated, site-directed mutagenesis assay to detect the two most common A1AT deficient variants, Z and S. By coamplification, using primers for both the Z and S mutations, we were able to detect heterozygous and homozygous genotypes for both mutations in a single reaction. We compared our results with phenotype studies obtained by standard immunofixation and isoelectric focusing techniques at two reference laboratories. Whereas PCR and isoelectric focusing agreed completely, there were five discrepancies in the results obtained by the immunofixation procedure. The reference laboratory that provided these discrepant results later informed us of a quality control problem that accounted for their error. The family study included 12 individuals representing three generations. Two individuals were MM homozygotes, three were MZ heterozygotes, four were MS heterozygotes, and three were SZ heterozygotes. A thirteenth family member was diagnosed as a ZZ homozygote at another institution. We have shown that this PCR coamplification technique provides accurate information about the M, S, and Z alleles that is at least as useful as current reference laboratory methodologies.

The effects of heparin on lipoproteins in high-resolution electrophoresis of serum

Sera from heparinized patients commonly display anodal slurring of both the alpha and beta lipoproteins when they are examined by high-resolution electrophoresis (HRE). In this study, the authors examined the effect of heparin and lipoprotein lipase on the electrophoretic migration of alpha and beta lipoproteins in sera. The addition of 10 to 1,000 units of heparin/mL to normal sera resulted in a concentration-dependent anodal slurring of the beta lipoproteins. At 40 units/mL, the beta lipoprotein band was not visible when the Paragon blue protein stain was used. The beta lipoprotein could be seen as a wide, faintly staining band with lipoprotein stain. The alpha lipoprotein band on the same gel was unaffected by the added heparin. High-resolution electrophoresis of other sera from patients who were therapeutically heparinized demonstrated anodal slurring of both alpha and beta lipoproteins independent of heparin concentration. Immunofixation electrophoresis (IFE) studies confirmed that apolipoproteins A and B were slurred within their respective bands. Heparin activates lipoprotein lipase with release of free fatty acids (FFA) from very low density lipoproteins and chylomicrons. To test this effect on migration, sera were incubated with lipoprotein lipase in vitro. The anodal slurring of both the alpha and beta lipoprotein was associated with the amount of FFA production. Individuals interpreting electrophoretic patterns should be aware that both the alpha and beta lipoproteins can migrate and slur anodally in heparinized patients. In addition, when the beta lipoprotein band interferes with the identification of monoclonal gammopathies, its migration can be selectively altered by the addition of 40 units/mL heparin to the sample.

Low maternal serum unconjugated estriol during prenatal screening as an indication of placental steroid sulfatase deficiency and X-linked ichthyosis

Placental sulfatase deficiency is an X-linked metabolic defect that occurs in about 1 in 2,000 to 5,000 males. It is associated with congenital ichthyosis. In this report, the authors document a case of placental sulfatase deficiency detected during routine prenatal screening of maternal serum by the triple test: serum alpha-fetoprotein (AFP), unconjugated estriol (uE3), and human chorionic gonadotropin (hCG). At 16-weeks gestation, her AFP was 20.9 IU/mL (multiple of the median [MOM] 0.83), hCG was 14.4 mIU/L (MOM 0.42) and her uE3 was 0.01 nmol/L (MOM 0.01). The extremely low uE3 indicated a possible placental sulfatase deficiency, congenital adrenal hypoplasia, or other unknown abnormality. On receiving this information, the obstetrician obtained a family history that was consistent with ichthyosis in the maternal grandfather and his siblings. Biochemical analysis of placenta documented the lack of sulfatase activity. This case illustrates that an extremely low level of maternal uE3 should prompt investigation of the family for evidence of X-linked ichthyosis associated with placental sulfatase deficiency.

Free light chains of immunoglobulins: clinical laboratory analysis

The increased sensitivity of immunofixation electrophoresis (IFE) over prior electrophoretic methods has led to renewed interest in the study of free light chains. Here, we discuss problems associated with the identification of monoclonal free light chains (Bence Jones proteins) in urine. Besides reviewing the nature of the sample specimens and the assays themselves, we discuss the physiology, biochemistry, genetics, and immunological properties of these molecules. Direct measurement of kappa/lambda ratios may ultimately be useful, but all commercial methods available now lack sufficient sensitivity. IFE is the preferred method because of its sensitivity and ease of interpretation. There are, however, difficulties associated with the interpretation of urinary IFE patterns, because the technique does not include an intrinsic mechanism for antibody-antigen titration and because of its great sensitivity in the absence of quantification. Problems of interpretation are discussed.

Free light chains of immunoglobulins: clinical laboratory analysis

The increased sensitivity of immunofixation electrophoresis (IFE) over prior electrophoretic methods has led to renewed interest in the study of free light chains. Here, we discuss problems associated with the identification of monoclonal free light chains (Bence Jones proteins) in urine. Besides reviewing the nature of the sample specimens and the assays themselves, we discuss the physiology, biochemistry, genetics, and immunological properties of these molecules. Direct measurement of kappa/lambda ratios may ultimately be useful, but all commercial methods available now lack sufficient sensitivity. IFE is the preferred method because of its sensitivity and ease of interpretation. There are, however, difficulties associated with the interpretation of urinary IFE patterns, because the technique does not include an intrinsic mechanism for antibody-antigen titration and because of its great sensitivity in the absence of quantification. Problems of interpretation are discussed.

Stimulation of gastrointestinal antibody to Shiga toxin by orogastric immunization in mice

Shiga toxin (ST) is a protein toxin of Shigella dysenteriae type 1, a causative agent of severe diarrhoea and dysentery. In this report we describe the gastrointestinal secretory antibody response of mice following orogastric immunization with ST. Gastrointestinal secretions were sampled by a gastrointestinal lavage technique weekly for 5 weeks after initial immunization. Assay of lavage samples by ELISA showed that mice vaccinated orogastrically with various doses of ST developed gastrointestinal antibody to ST in a dose-dependent manner. Serum anti-ST activity developed by 5 weeks after initial immunization. The ability of ST to act as a mucosal immune adjuvant was investigated by coadministration of ST and keyhole limpet haemocyanin. In contrast to cholera toxin, a potent adjuvant, ST did not demonstrate adjuvant activity. The mouse gastrointestinal lavage model could be useful for further analysis of the cellular basis of ST immunogenicity.

Coagulation disorders in patients with monoclonal gammopathies

Monoclonal gammopathies can present as disorders of coagulation whether the gammopathy is due to a malignant B-cell lymphoproliferative disorder or a monoclonal gammopathy of undetermined significance. Detection of the monoclonal gammopathy involves quantification of immunoglobulins including kappa and lambda along with high-resolution electrophoresis of serum. Immunofixation is occasionally needed on serum and always needed on urine for the final diagnosis.