Effect of linoleic acid, linoleic acid anilide, and arachidonic acid on the expression of adhesion molecules on human neutrophils

The effects of linoleic acid, linoleic acid anilide, and arachidonic acid on the expression of CD11b/ CD18, CD11c/CD18 integrins and L-selectin on human neutrophils were studied by flow cytometry in a whole blood assay. None of these compounds had any effect on the basal expression of CD11b, CD11c, or L-selectin in the concentration range of 20-100 microM. However, linoleic acid at a concentration of 1000 microM slightly up-regulated CD11b and CD11c by a factor of 2.1 and 1.7, respectively. Linoleic acid, linoleic acid anilide, and arachidonic acid did not affect the formyl-methionyl-leucyl-phenylalanine induced up-regulation of CD11b or CD11c. However, linoleic acid and linoleic acid anilide slightly inhibited the phorbol myristate acetate (PMA)-induced expression of CD11b, which was decreased by 27 and 21% at concentrations of 100 and 1000 microM, respectively. Likewise, arachidonic acid at 40 microM inhibited the PMA-induced expression of CD11b by 19%. Our results suggest that linoleic acid, linoleic acid anilide, and arachidonic acid do not dramatically affect the expression of leukocyte adhesion molecules in a whole blood assay.

A new class of obesity genes encodes leukocyte adhesion receptors

Obesity is a complex disease, and multiple genes contribute to the trait. The description of five genes (ob, db, tub, Ay, and fat) responsible for distinct syndromes of spontaneous monogenic obesity in mice has advanced our knowledge of the genetics of obesity. However, many other genes involved in the expression of this disease remain to be determined. We report here the identification of an additional class of genes involved in the regulation of adipose tissue mass. These genes encode receptors mediating leukocyte adhesion. Mice deficient in intercellular adhesion molecule-1 became spontaneously obese in old age on normal mouse chow or at a young age when provided with a diet rich in fat. Mice deficient in the counterreceptor for intercellular adhesion molecule-1, the leukocyte integrin alphaMbeta2 (Mac-1), showed a similar obesity phenotype. Since all mice consumed approximately the same amount of food as controls, the leukocyte function appears to be in regulating lipid metabolism and/or energy expenditure. Our results indicate that (i) leukocytes play a role in preventing excess body fat deposition and (ii) defects in leukocyte adhesion receptors can result in obesity.

Regulation of expression of the LFA-1 and p150,95 leukocyte integrins: involvement of the CD11a and CD11c gene promoters

Human Lymphocyte Associated Antigen-1 (LFA-1, CD11a/CD18, alpha L/beta 2) and p150,95 (CD11c/CD18, alpha X/beta 2) are cell surface alpha/beta heterodimers that, together with Mac-1 (CD11b/CD18, alpha M/beta 2) comprise the leukocyte-restricted beta 2 subfamily of integrins. LFA-1 is the only integrin expressed on all leukocyte lineages while p150,95 is exclusively expressed on cells of the myeloid lineage and on activated B lymphocytes and natural killer cells. The expression of the leukocyte integrins is regulated during cell activation and differentiation by transcriptional mechanisms. To dissect the molecular basis for the tissue-restricted and developmentally regulated expression of LFA-1 and p150,95, the promoter regions of their corresponding alpha subunits (CD11a and CD11c) were isolated and functionally characterized. Both promoters lack TATA and CAAT boxes, but exhibit initiator-like sequences at their major transcriptional start sites. Transient expression of CD11a- and CD11c-based reporter gene constructs have demonstrated the involvement of both promoters in the tissue-specific expression of LFA-1 and p150,95. Furthermore, a combination of DNAse I protection experiments and mobility band shift assays have revealed the existence of numerous DNA-protein interactions at the proximal region of both promoters, some of which overlap with consensus binding sequences for known transcription factors and correlate with the pattern of expression of both integrins.

Leukocyte adhesion deficiency: recurrent childhood skin infections

Leukocyte adhesion deficiency is a rare autosomal recessive disorder caused by the absent or severely reduced cell surface expression of a subfamily of leukocyte integrin molecular (beta 2 leukocyte integrins, CD11a/CD18, CD11b/CD18, CD11c/CD18). These molecules are required for the normal processes of leukocyte adherence and chemotaxis. Patients often die during the first years of life of a severe bacterial or fungal infection. We describe a 13-year-old boy with leukocyte adhesion deficiency who had intermittent cutaneous infections that were recalcitrant to treatment. Except for periodontitis, he had no other clinical problems. The diagnosis of leukocyte adhesion deficiency should be considered in patients with recurrent cutaneous infections that do not respond well to therapy, even in the absence of more serious manifestations. Evaluation should include flow cytometry studies to detect surface expression of the beta 2 leukocyte integrins on both resting and activated polymorphonuclear leukocytes.

CD11b/CD18 expression, adherence, and chemotaxis of granulocyte in adult respiratory distress syndrome

The accumulation of granulocytes in the pulmonary microvasculature is generally thought a cardinal event in the pathology of adult respiratory distress syndrome (ARDS). However, the mechanism by which granulocytes are sequestered in the pulmonary vascular bed remains largely unknown. Because the CD11b/CD18 membrane receptors mediate various adhesion-dependent functions, their expression was investigated in granulocytes from patients during the course of ARDS development in relation to adherence and chemotaxis. CD11b expression of ARDS resting granulocytes was increased within 24 h of ARDS onset by a factor of two in comparison with control patients (p < 0.05) and remained significantly increased 72 to 120 h later. In contrast, the stimulated expression was significantly decreased only within 24 h of ARDS onset. Adherence was not modified within 8 h of the onset of ARDS, but was increased at Days 1, 3, and 5. The time course of granulocyte chemotaxis shows a decreased chemotaxis capacity during the first 3 d of ARDS, followed by normalization at Day 5. The dynamic changes observed in the various functions studied indicate a possible relationship between the modulation of the CD11b expression and a hyperadhesive state of granulocytes in ARDS. These sticky granulocytes may potentially contribute to the microvascular injury.

Investigation of the polymorphic AvaII site by a PCR-based assay at the human CD18 gene locus

The AvaII polymorphic site within the human CD18 gene was investigated in the Japanese population. A distinct distribution pattern is observed in this population. This polymorphism provides a new genetic marker for the long arm of chromosome 21 and should be a useful marker of leukocyte adhesion deficiency caused by mutations of the CD18 gene.

The human beta 2 integrin CD18 promoter consists of two inverted Ets cis elements

To define the minimal promoter responsible for expression of CD18 in myeloid and lymphoid cells, we generated 5' and 3' deletion constructs of a segment extending 785 bp upstream and 19 bp downstream of a major transcription start site and determined their effects on driving expression of the luciferase reporter gene in transfected hematopoietic cell lines. A region extending from nucleotides (nt) -302 to +19 was sufficient for cell-restricted and phorbol ester-inducible expression. DNase I footprinting of this region revealed two adjacent protected segments extending from nt -81 to -68 (box A) and -55 to -41 (box B). When a construct of 47 nt in length containing box A and box B and lacking other 3' or 5' elements was cloned into a promoterless vector, it conferred tissue-specific and phorbol ester-inducible expression. Gel retardation revealed that the protein components of two major protein-DNA complexes that form on both box A and box B and are required for transcriptional activation are members of the Ets oncoprotein family; one is related to the GA-binding protein (GABP), and the other is related to PU.1/Spi-1. The minimal CD18 promoter, lacking TATA, CAAT, and initiator elements and consisting primarily of Ets repeats, may exemplify an emerging class of promoters with which the concerted binding of Ets factors is necessary and sufficient to mediate transcriptional activation through direct recruitment of the basal transcription machinery.

Neurtrophil function and pathologic findings in Holstein calves with leukocyte adhesion deficiency

Leukocyte adhesion deficiency was diagnosed in 4 Holstein calves from 1 to 4 months old. Calves had severe ulcers on oral mucous membranes, gingivitis, severe periodontitis, chronic pneumonia, and stunted growth associated with severe neutrophilia. Neutrophils from affected calves had function defect, characterized by severely decreased adherence, chemotactic movements, phagocytosis, luminol-dependent chemiluminescent response, and O(2-)-producing activities. Deficient CD18 expression (0.1 to 1.7%) on neutrophils was clearly detected by use of flow cytometric analysis. These affected calves were linked to a common ancestral sire that has been documented to be a carrier. Clinical features, leukocyte functional abnormalities, deficient expression of CD18, and mode of inheritance indicated that affected calves had leukocyte adhesion deficiency. In vitro leukocyte functional abnormalities were associated with deficiency in the expression of CD11/CD18. Pathologic findings indicated possible increased susceptibility to infection associated with this disease.

Bovine leukocyte adhesion deficiency in Holstein cattle

Two Holstein heifers with persistent and recurrent infections including ulcerative gingivitis, periodontitis, pneumonia, loss of teeth and stunted growth associated with marked neutrophilia were evaluated clinically and for neutrophil function, CD18 expression on neutrophils and CD18 genotype analysis by DNA-polymerase chain reaction (PCR) test. Adherence to nylon fibers and phagocytic activity of neutrophils from affected animals were significantly (p < 0.05) impaired as compared with those of controls. Neutrophils from affected heifers had decreased chemiluminescent (CL) responses when stimulated with opsonized zymosan, compared with those of controls. In contrast, neutrophils from affected heifers produced increased CL responses when stimulated with latex beads and phorbol myristate acetate compared with those of controls. The clinical findings, functional leukocyte abnormalities, deficiency in expression of CD18 on neutrophils, and the D128G mutation detected by DNA-PCR testing of affected heifers demonstrated that these heifers have bovine leukocyte adhesion deficiency (BLAD). Although both animals were confirmed to be homozygotes for BLAD by DNA-PCR test, they had differences in clinical, hematological and neutrophil functional characteristics.

Retroviral mediated expression of CD18 in normal and deficient human bone marrow progenitor cells

The CD18 gene encodes the beta subunit of leukocyte integrins, and autosomal recessive deficiency of CD18 in humans causes a life-threatening abnormality of granulocyte migration. A high titer amphotropic retrovirus encoding CD18 was used to infect bone marrow cells from normal and CD18-deficient human donors. Infected cells were maintained in a long-term culture system and analyzed (1) using PCR to detect the provirus in granulocyte or macrophage colonies (CFU-GMs) derived from the culture, (2) using reverse transcription-PCR (RT-PCR) to detect transcripts in the floating cells in the culture, and (3) using immunostaining of the floating cells to analyze expression of human CD18. By both cocultivation and supernatant infection, a significant fraction (10-82%) of the CFU-GMs were positive for the provirus after five weeks in long-term culture, and as high as 10-15% of the floating cells were positive by immunostaining after nine weeks in the long-term culture. In all cases, cocultivation showed higher infection efficiency than supernatant infection. This is the first report of the introduction of human CD18 cDNA into the bone marrow progenitor cells of patients with leukocyte adhesion deficiency.

A point mutation associated with leukocyte adhesion deficiency type 1 of moderate severity

Leukocyte adhesion deficiency (LAD) is a genetic disease characterized clinically by severe bacterial infections, and biochemically by a deficiency in the surface expression of the CD11/CD18 leukocyte integrins. We studied a teenage girl with the moderate deficiency phenotype of LAD. B-lymphoblastoid cells from this patient displayed approximately 5% of normal levels of CD11/CD18 on the cell surface. Although a normal sized CD18 mRNA was detectable on Northern blotting, a small CD18 protein was present on Western blotting. Sequencing of the RNA revealed a single base pair substitution resulting in a glycine to serine amino acid substitution at amino acid 284. This amino acid substitution occurs within a highly conserved region of the extracellular domain of CD18 in which several other mutations have been identified in LAD.

Expression of human CD18 in murine granulocytes and improved efficiency for infection of deficient human lymphoblasts

The CD18 gene encodes the beta 2-subunit of leukocyte integrins, and mutations in this gene cause extreme host susceptibility to bacterial and fungal infection. Because expression of CD18 is restricted to bone marrow-derived cells, this disorder is considered an excellent candidate for somatic gene therapy utilizing ex vivo infection of bone marrow stem cells. We have constructed a retroviral vector expressing CD18 with the Moloney murine leukemia virus (Mo-MLV) long terminal repeat (LTR) as the promoter, and high-titer ecotropic and amphotropic producer cell lines were isolated using the GP+E-86 and GP+envAM12 safe packaging cell lines. Infection of CD18-deficient lymphoblasts resulted both in expression of immunodetectable CD18 at 35-40% of normal levels on 55-60% of cells and in functional restoration of CD18-dependent aggregation. All of 16 mice transplanted with syngeneic bone marrow infected with the CD18 retrovirus expressed human CD18 on 17-36% of granulocytes at 2 weeks after transplantation, and expression was appropriately up-regulated in response to stimulation with zymosan-activated serum. This recombinant retrovirus should prove useful for further studies of somatic gene therapy for CD18 deficiency.

The detection of a mutation of CD18 gene in bovine leukocyte adhesion deficiency (BLAD)

Two calves (5 and 9 months old) affected with pneumonia and gingivitis were also diagnosed as having bovine leukocyte adhesion deficiency (BLAD). The gene of leukocyte adhesion molecule CD18 in these BLAD calves and their dams (carrier) were examined by means of polymerase chain reaction (PCR) and digestion of restriction endonuclease. The splicing in mRNA coded CD18 reported in human LAD was not recognized in BLAD on the basis of the results of PCR amplification. The region including the portion of point mutation, which corresponded to the region reported in the human patient, was amplified by PCR, and the PCR product was then digested with Taql. An obvious difference was recognized in the pattern of digestion among healthy calves, BLAD calves and their dams. In BLAD, therefore, the point mutation reported in human patients was strongly suggested. Moreover it may be a method able to be used in detecting the carrier.

Characterization of the p150,95 leukocyte integrin alpha subunit (CD11c) gene promoter. Identification of cis-acting elements

The leukocyte integrin p150,95 (CD11c/CD18) is involved in a number of cell-cell and cell-extracellular matrix interactions and mediates signal transduction into the cytoplasm. p150,95 is expressed on cells of the myeloid lineage as well as on certain activated T and B lymphocytes, and its expression is regulated during cell activation and differentiation. Since CD18 is expressed on all leukocyte lineages, the restricted expression of p150,95 must be controlled at the level of CD11c gene transcription. To understand the mechanisms that direct the constitutive and regulated leukocyte expression of p150,95 we have structurally characterized the CD11c promoter region and initiated its functional dissection. The CD11c promoter lacks TATA- and CCAAT-boxes, directs the synthesis of transcripts with heterogeneous 5'-ends, and contains an initiator-like sequence at the major transcription initiation site. Several putative binding sequences for ubiquitous (Sp1, AP-1, AP-2, and NF-kB) and leukocyte-specific (PU.1) transcription factors have been identified in the proximal region of the CD11c promoter which may participate in the regulation of the expression of p150,95. Transient expression of CD11c-based reporter gene constructs indicates that the CD11c promoter dictates the tissue-specific expression of p150,95 and that sequences contained within 160 base pairs 5' from the major transcriptional start site are involved in the tissue-specific and regulated expression of p150,95. DNase I protection analysis on the promoter region spanning from -160 to +40 revealed four regions of DNA-protein interactions (FPI-FPIV), two of which (FPII and FPIV) correlate with the cell type-specific and regulated expression of the CD11c gene.

Bovine leukocyte adhesion deficiency in Danish Holstein-Friesian cattle. II. Patho-anatomical description of affected calves

The patho-anatomical findings in 3 Danish Holstein-Friesian calves affected with bovine leukocyte adhesion deficiency (BLAD) are described. The diagnosis was confirmed by genotyping for the BLAD mutagene by polymerase chain reaction technique. The main clinical symptoms were general unthriftyness and leukocytosis with a high proportion of neutrophils. None of the calves suffered from severe infections and the major pathological changes were different from those described in previously published cases. One calf had a fibro-granulomatous perilienitis and calcification of splenic stroma and pulmonic arteries. In the other cases only minor pathological changes were present.

Bovine leukocyte adhesion deficiency in Danish Holstein-Friesian cattle. I. PCR screening and allele frequency estimation

A screening program for bovine leukocyte adhesion deficiency (BLAD) in Danish Holstein-Friesian cattle has been initiated. During the first months 1611 animals were tested by a PCR based assay. Of these animals 1256, 346, and 8 were assigned normal, BLAD carriers, and BLAD affected animals, respectively. One bull, born as a co-twin, showed weak reaction for the BLAD allele on DNA isolated from leukocytes, but a normal genotype on DNA isolated from semen. Chromosome analysis showed that this bull was a blood chimaera. Estimation of the BLAD allele frequency upon the PCR test results showed that around 450 Danish calves born in 1991 might have been affected with the recessive disorder.

Identification and prevalence of a genetic defect that causes leukocyte adhesion deficiency in Holstein cattle

Two point mutations were identified within the gene encoding bovine CD18 in a Holstein calf afflicted with leukocyte adhesion deficiency (LAD). One mutation causes an aspartic acid to glycine substitution at amino acid 128 (D128G) in the highly conserved extracellular region of this adhesion glycoprotein, a region where several mutations have been found to cause human LAD. The other mutation is silent. Twenty calves with clinical symptoms of LAD were tested, and all were homozygous for the D128G allele. In addition, two calves homozygous for the D128G allele were identified during widespread DNA testing, and both were subsequently found to exhibit symptoms of LAD. The carrier frequency for the D128G allele among Holstein cattle in the United States is approximately 15% among bulls and 6% among cows. This mutation is also prevalent among Holstein cattle throughout the world, placing this disorder among the most common genetic diseases known in animal agriculture. All cattle with the mutant allele are related to one bull, who through the use of artificial insemination sired many calves in the 1950s and 1960s. The organization of the dairy industry and the diagnostic test described herein will enable nearly complete eradication of bovine LAD within 1 year. These results also demonstrate that bovine LAD is genetically homologous and phenotypically similar to human LAD, thus providing a useful animal model for studies of LAD and beta 2 integrin function.

Leucocyte adhesion protein deficiency in Irish setter dogs

Investigation of 12 Irish setter puppies from six litters with severe recurrent infections, neutrophilia and low body weight revealed a leucocyte adhesion protein deficiency with a total lack of CD11b and CD18. Their neutrophil function was severely impaired with a totally absent capacity to ingest C3b-opsonized particles, a significantly impaired capacity to ingest IgG-opsonized particles and significantly diminished adherence to nylon wool when compared with neutrophils from healthy control dogs. The chemiluminescence of patient neutrophils activated by C3b-opsonized particles was, consequently, significantly decreased compared with that of control neutrophils, while the respiratory burst assayed by phorbolmyristate acid (PMA) stimulated nitroblue tetrazolium (NBT)-reduction was normal in the patient group. Random migration and chemotactic responses of patient and control neutrophils, were similar. The etiology, pathogenesis and clinical manifestations of the Irish setter leucocyte adhesion deficiency were similar to that of the leucocyte adhesion deficiency in humans.

Cloning and analysis of the CD18 promoter

CD18, the common beta chain of the leukocyte integrin adhesion proteins, is expressed exclusively by myeloid cells and lymphocytes. During myeloid differentiation, the increase in CD18 cell surface expression is paralleled by increased CD18 messenger RNA levels. Nuclear run-on studies show that CD18 expression is transcriptionally regulated during 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced HL-60 monocytic differentiation. The CD18 transcriptional start site was defined by primer extension and RNAse protection. The gene encoding CD18 was cloned and a fragment that overlaps the transcriptional start site was isolated. DNA sequence analysis of this promoter fragment identified potential AP-1 elements that may mediate the TPA transcriptional response. The CD18 promoter also contains a putative binding site for PU.1, a leukocyte-specific transcription factor. DNA elements resembling those found in other myeloid and integrin promoters were identified. The CD18 promoter fragment was linked to the luciferase reporter gene, electroporated into the U937 monocytic cell line, and its expression increased after exposure to TPA. Thus, CD18 may serve as a model for identifying the cis elements and trans-acting factors that regulate gene expression during myeloid differentiation.

Sequence of the bovine CD18-encoding cDNA: comparison with the human and murine glycoproteins

The bovine cDNA (CD18) encoding CD18, a cell-surface glycoprotein involved in multiple leukocyte functions, was sequenced and compared with the human and murine sequences. Portions of the 5'- and 3'-untranslated regions of the nucleotide sequences are conserved among the three species, including a 3' A+T-rich region believed to regulate mRNA stability and translational efficiency. The 2833-bp bovine sequence coded for a protein of 769 amino acids (aa). Overall, the deduced aa sequences were greater than 80% identical among the three species. The aa 96-389 and those in the cytoplasmic domain were very highly conserved with approx. 95% aa identity. All Cys residues and potential Asn-glycosylation sites present in the bovine sequence were also present in the human and murine sequences. The aa identity was also found in those regions where mutations were found to cause the genetic disease, leukocyte adhesion deficiency. These data identify functionally important regions of the CD18 mRNA and protein.

Genetic cause of leukocyte adhesion molecule deficiency. Abnormal splicing and a missense mutation in a conserved region of CD18 impair cell surface expression of beta 2 integrins

Patients with leukocyte adhesion molecule (CD11/CD18, beta 2 integrins) deficiency have structural defects in the common beta subunit (CD18), which prevent heterodimer formation and normal cell surface expression of these receptors, leading to life-threatening bacterial infections. To elucidate the nature of these defects in a patient with partial (type II) deficiency, abnormal CD18 cDNA clones were isolated, using the polymerase chain reaction to amplify the patient's B cell-derived cDNAs. Sequence analysis revealed two mutant alleles. cDNA clones, representing a maternal allele, contained both a 12-base pair insertion resulting in an in-frame addition of four amino acids between P247 and E248 and a C1756----T nucleotide transition, resulting in an R586----W substitution in the normal CD18 protein. The inframe insertion arose by a single nucleotide C----A transversion in the 3' terminus of an intron, generating aberrant splice acceptor site. Other cDNA clones contained an A1052----G nucleotide transition not present in either parent which resulted in an N351----S substitution. To determine the functional importance of these changes, cDNA encoding a normal alpha chain (CD11b) was cotransfected into COS with CD18 cDNAs encoding for wild-type, maternal mutant allele, or CD18 containing N351----S substitution. Immunostaining of transfectants with anti-CD18 monoclonal antibodies revealed no cell surface expression of the maternal mutant CD18, and 22% surface expression of N351----S CD18. Both the insertion and the N351----S mutations occurred in a 250 amino acid extracellular region of CD18 that is highly conserved among beta integrins supporting a role for this region in heterodimer formation.

Identification and sequence analysis of the promoter for the leukocyte integrin beta-subunit (CD18): a retinoic acid-inducible gene

Leukocyte adhesion receptors (LFA-1; Mac-1; p150,95) are a family of heterodimeric cell-surface adhesion molecules expressed exclusively in granulocytes, lymphocytes, and macrophages. Expression of these proteins is under complex regulatory control, but to date promoters for these genes have not been identified. The CD18 gene codes for the common beta-subunit of the leukocyte adhesion receptors. Transcription of CD18 is highly tissue-specific, hormonally inducible (by retinoic acid [RA]), and coordinately regulated with leukocyte integrin alpha-chains. To identify the CD18 promoter, we screened a human genomic phage library with a human CD18 cDNA probe and obtained a clone that contains an exon coding for the 5' untranslated region (UTR). Using rapid amplification of cDNA ends (RACE), RNAse protection, S1 nuclease, and primer extension assays, we demonstrated the existence of multiple transcription start sites clustered in a 45-nt region. We investigated the transcription-promoting activity of the genomic sequences 5' to the CD18 gene by performing transient expression assays with a growth hormone reporter gene in various hematopoietic cell lines. The CD18 promoter was active in Jurkat cells, a lineage that normally expresses CD18 but was considerably less active in K562, an early erythroid line that does not normally express CD18. The genomic sequences upstream of the start site cluster lack CAAT and TATA boxes, but have two Sp1 binding sites and 10 T(G/C)AC(C/A) boxes, which may represent binding sites for RA receptors (RAR). These features distinguish the CD18 promoter from the promoters of other tissue-specific, hormone-inducible genes, and may be representative of leukocyte integrin promoters in general.

An initiation codon mutation in CD18 in association with the moderate phenotype of leukocyte adhesion deficiency

Leukocyte adhesion deficiency (LAD) is an autosomal recessive disease caused by mutations in the CD18 gene which codes for the beta 2 integrin subunit. We studied two patients, the first of which had a moderate LAD phenotype and expressed only 9% of CD11/CD18 on blood leukocytes. RNA from lymphoblasts was reverse-transcribed, and the cDNA was amplified, cloned, and sequenced. An ATG to AAG alteration in the initiation codon was detected in 39 of 45 (87%) cDNA clones. This mutation was detected in the father, but not in the mother. The maternal defect was shown to be a frameshift mutation with the deletion of a single T in the aspartic acid codon at position 690 (GAT), 11 amino acids N-terminal to the beginning of the transmembrane domain. This mutation predicts a polypeptide which would terminate without transmembrane or cytoplasmic domains. The frameshift mutation was also found in the second patient who had the severe phenotype of LAD (less than 1% of CD11/CD18), indicating that this allele does not encode a functional protein. The partial expression in the patient with a moderate phenotype must be derived from the initiation codon mutation and may be due to a low level of initiation of translation of the CD18 mRNA at the second codon (CUG).

Gold treatment of rheumatoid arthritis decreases synovial expression of the endothelial leukocyte adhesion receptor ELAM-1

Leukocyte adhesion receptors on endothelial cells play an important role in the evolution of synovitis. We studied sequential synovial biopsies at Weeks 0, 2 and 12 in 11 patients with rheumatoid arthritis beginning parenteral gold therapy either alone or combined with 120 mg intramuscular methylprednisolone acetate at Weeks 0, 4 and 8 of treatment. Expression of endothelial leukocyte adhesion molecule 1 (ELAM-1) decreased on synovial blood vessels after both 2 and 12 weeks treatment (p less than 0.05), while the overall vascularity of the synovium did not change. Neutrophil numbers within the synovial membrane also decreased although this did not reach statistical significance. In contrast, there was no significant change in numbers or subset distribution of T cells or in Class II MHC expression by synovial lining cells, mononuclear cells or endothelial cells. Our results suggest that one of the early effects of intramuscular gold and glucocorticoid therapy may be a downregulation of the acute inflammatory process associated with the endothelial expression of a neutrophil adhesion receptor and the subsequent recruitment of neutrophils into the joint.

Molecular mapping of functional domains of the leukocyte receptor for endothelium, LAM-1

The human lymphocyte homing receptor LAM-1, like its murine counterpart MEL-14, functions as a mammalian lectin, and mediates the binding of leukocytes to specialized high endothelial cells in lymphoid organs (HEV). LAM-1 is a member of a new family of cell adhesion molecules, termed selectins or LEC-CAMs, which also includes ELAM-1 and PAD-GEM (GMP-140/CD62). To localize the regions of LAM-1 that are involved in cell adhesion, we developed chimeric selectins, in which various domains of PAD-GEM were substituted into LAM-1, and used these chimeric proteins to define the domain requirements for carbohydrate binding, and to localize the regions recognized by several mAb which inhibit the adhesion of lymphocytes to lymph node HEV. The binding of PPME or fucoidin, soluble complex carbohydrates that specifically define the lectin activity of LAM-1 and MEL-14, required only the lectin domain of LAM-1. The LAM1-1, LAM1-3, and LAM1-6 mAb each strongly inhibit the binding of lymphocytes to HEV in the in vitro frozen section assay, and defined three independent epitopes on LAM-1. Blocking of PPME or fucoidin binding by LAM1-3 indicated that this site is identical, or in close proximity, to the carbohydrate binding site, and analysis of the binding of LAM1-3 to chimeric selectins showed that the epitope detected by LAM1-3 is located within the lectin domain. Although the LAM1-6 epitope is also located in the lectin domain, LAM1-6 did not affect the binding of PPME or fucoidin. The LAM1-1 epitope was located in, or required, the EGF domain, and, importantly, binding of LAM1-1 significantly enhanced the binding of both PPME and fucoidin. These results suggest that adhesion mediated by LAM-1 may involve cooperativity between functionally and spatially distinct sites, and support previous data suggesting a role for the EGF domain of LAM-1 in lymphocyte adhesion to HEV.

Expression of a soluble and functional form of the human beta 2 integrin CD11b/CD18

Polymorphonuclear cells and monocytes (phagocytes) are a critical component of host defense against infections. However, these cells also play a significant role in host tissue damage in many noninfectious diseases, such as ischemia-reperfusion injury syndromes and rejection of transplanted organs. The leukocyte adhesion molecule family CD11/CD18 (beta 2 integrins) is critical to the function of polymorphonuclear cells and monocytes in inflammation and injury. Inherited deficiency of CD11/CD18 impairs phagocyte chemotaxis, adhesion and transmigration across endothelium, and clearance of invading microorganisms through phagocytosis and cell-mediated killing. Furthermore, murine monoclonal antibodies directed against the CD11b/CD18 (CR3) heterodimer have been shown to reduce, by 50%-80%, phagocyte-mediated ischemia-reperfusion injury in several organ systems, such as the myocardium, liver, and gastrointestinal tract and to inhibit development of insulin-dependent diabetes mellitus in nonobese diabetic (NOD) mice. Expression of CD11b/CD18 in a soluble and functional form might therefore be potentially useful as an anti-inflammatory agent. We have now expressed a recombinant soluble heterodimeric form of this human beta 2 integrin, normally expressed as two noncovalently associated membrane-bound subunits. The secreted receptor exhibited direct and specific binding to its ligand, iC3b, the major complement C3 opsonin, and inhibited binding of polymorphonuclear cells to recombinant interleukin 1-activated endothelium.

Expression of the CD11/CD18, leukocyte adhesion molecule 1, and CD44 adhesion molecules during normal myeloid and erythroid differentiation in humans

We have used three-color flow cytometry to investigate the pattern of expression of the CD11/CD18, CD44, and leukocyte adhesion molecule 1 (LAM-1) adhesion molecules during myeloid and erythroid differentiation in humans. The earliest myeloid cells, identified as CD33loCD15-, were exclusively CD44hi but contained both leukocyte function-associated antigen 1 (LFA-1hi) and LFA-1lo cells, as well as LAM-1+ and LAM-1- cells. This CD33loCD15- myeloid subpopulation expressed only low levels of CD11c and failed to express CD11b, CD14, or any lymphoid (CD3, CD16, CD19) antigens or glycophorin. Commitment to monocyte differentiation, suggested by the presence of an LFA-1hi CD11c+ subset within the CD33loCD15- subpopulation, was clearly signaled by upregulation of CD33; these monocyte-lineage committed cells were exclusively CD33hi, CD44hi, CD11ahi, CD11c+, and exhibited a broad range of intensity of CD15 expression. Later stages of monopoiesis were identified by acquisition of CD11b, and subsequently of CD14. Myeloid cells committed to granulopoiesis remained LFA-1lo, and underwent a sharp upregulation of CD15 along with downregulation of both CD33 and CD44. Successive stages of granulocyte development were marked by expression of CD11b and, subsequently, of CD16. The earliest cells capable of erythroid differentiation were CD44hi, LFA-1lo, and LAM-1+. Both LFA-1 and LAM-1 were lost before the onset of glycophorin (glyco) expression, whereas CD44 expression remained high on glyco+ cells, which also expressed CD45. CD44 expression was intermediate on glyco+ CD71+ cells, and low on glyco+ CD45- CD71- cells, similar to normal, circulating erythrocytes. Our results allow us to phenotypically define discrete stages in the normal development of monocytes, neutrophils, and erythrocytes. The expression of LFA-1, LAM-1, and high levels of CD44 on the most primitive hematopoietic cells detectable by flow cytometry suggests that at least some of these molecules are critically involved in leukocyte adhesion during development.

Lymphocyte HEV adhesion variants differ in the expression of multiple gene sequences

Lymphocyte adhesion to high endothelial venule cells in lymphoid organs of mice is mediated by several cell-surface glycoproteins, one of which, gp90MEL-14, is detected by the MEL-14 monoclonal antibody (mAb). The MEL-14 mAb was used to select two variants of the EL4 cell line, EL4MEL-14-hi and EL4-MEL-14-lo, that have disparate cell surface expression of this adhesion receptor. A cDNA library constructed from EL4MEL-14-hi mRNA was enriched for sequences present at higher levels in EL4MEL-14-hi cells than EL4MEL-14-lo cells. Quantitative analysis of candidate differential clones by RNA probe protection methods identified five clones whose steady-state mRNA levels were increased in the EL4MEL-14-hi cells. One of these clones, DIFF6, is derived from an RNA whose expression level is higher in several cell lines producing high amounts of MEL-14-reactive gp90, and absent or present at lower levels in several cell lines expressing low levels of this glycoprotein. However, DIFF6 does not encode gp90MEL-14. The nucleotide sequence of this clone predicts a relatively hydrophilic protein characteristic of a cytoplasmic or nuclear protein. Present experiments indicate that expression of gp90MEL-14, a cell-surface-adhesion receptor molecule, may be coregulated with additional cytoplasmic or nuclear factors.

Distinct mutations in two patients with leukocyte adhesion deficiency and their functional correlates

Two patients with leukocyte adhesion deficiency (LAD), one with a moderate phenotype (patient 14) and one with a severe phenotype (patient 2) who had been shown to have a normal sized beta subunit protein precursor, were analyzed in an attempt to determine the molecular basis for their disease. RNase mapping located possible mutations to two distinct but adjacent regions of the beta subunit cDNA. Sequencing of patient-derived cDNA clones in this region revealed a C for T difference at amino acid 149 in patient 14 which resulted in the substitution of a leucine for a proline, and an A for G substitution at amino acid 169 in patient 2 which mutated a glycine to an arginine. The mutated amino acids are in a region of the cDNA that is highly conserved between the beta subunits of the integrin family and are identical in all known integrin beta subunits. Co-transfection of the beta subunit cDNA containing the patient 2 mutation with the wild-type alpha subunit of LFA-1 in a mammalian expression system resulted in no expression of LFA-1. In the case of the mutation in patient 14 there was markedly diminished expression of LFA-1 with loss of function and loss of the epitope for a number of anti-beta mAbs. Normal half-life of the mutant beta subunits, and previous demonstration of a lack of alpha/beta complex formation during biosynthesis in patient cells, suggest a defect in association with the alpha subunit. Association with beta is required for expression of the alpha subunit of LFA-1. Loss of functional expression with both of these beta subunit mutations suggests that they lie in a site critical for association with the alpha subunit.

Correction of CD18-deficient lymphocytes by retrovirus-mediated gene transfer

Leukocyte adhesion deficiency (LAD) is an inherited disorder of leukocyte function caused by derangements in CD18 expression. The genetic and functional abnormalities in a lymphocyte cell line from a patient with LAD have been corrected by retrovirus-mediated transduction of a functional CD18 gene. Lymphocytes from patients with LAD were exposed to CD18-expressing retrovirus and enriched for cells that express CD11a and CD18 (LFA-1) on the cell surface. Molecular and functional analyses of these cells revealed (i) one copy of proviral sequence per cell, (ii) viral-directed CD18 RNA that exceeded normal endogenous levels, (iii) normal quantities of CD11a and CD18 protein on the cell surface, and (iv) reconstitution of LFA-1-dependent adhesive function.

Retinoic acid-induced granulocytic differentiation of HL-60 myeloid leukemia cells is mediated directly through the retinoic acid receptor (RAR-alpha)

Retinoic acid (RA) induces terminal granulocytic differentiation of the HL-60 promyelocytic leukemia cell line as well as certain other human myeloid leukemias. Specific RA receptors that are members of the steroid-thyroid hormone superfamily of nuclear transcription factors have recently been identified. We developed an HL-60 subclone that was relatively resistant to RA-induced differentiation. Specific nuclear RA receptors in this RA-resistant subclone had a decreased affinity for RA and exhibited a lower molecular weight compared with nuclear RA receptors from the RA-sensitive parental HL-60 cells. Retroviral vector-mediated transduction of a single copy of the RA receptor (RAR-alpha) into this RA-resistant HL-60 subclone restored the sensitivity of these cells to RA. These observations indicate that RAR-alpha plays a critical and central role in mediating RA-induced terminal differentiation of HL-60 leukemia cells.

Point mutations impairing cell surface expression of the common beta subunit (CD18) in a patient with leukocyte adhesion molecule (Leu-CAM) deficiency

The leukocyte adhesion molecules CD11a/CD18, CD11b/CD18, and CD11c/CD18 (Leu-CAM) are members of the integrin receptor family and mediate crucial adhesion-dependent functions in leukocytes. The molecular basis for their deficient cell surface expression was sought in a patient suffering from severe and recurrent bacterial infections. Previous studies revealed that impaired cell surface expression of Leu-CAM is secondary to heterogeneous structural defects in the common beta subunit (CD18). Cloning and sequencing of complementary DNA encoding for CD18 in this patient revealed two mutant alleles, each representing a point mutation in the coding region of CD18 and resulting in an amino acid substitution. Each mutant allele results in impaired CD18 expression on the cell surface membrane of transfected COS M6 cells. One substitution involves an arginine residue (Arg593----cysteine) that is conserved in the highly homologous fourth cysteine-rich repeats of other mammalian integrin subfamilies. The other substitution involves a lysine residue (Lys196----threonine) located within another highly conserved region in integrins. These data identify crucial residues and regions necessary for normal cell surface expression of CD18 and possibly other integrin beta subunits and define a molecular basis for impaired cell surface expression of CD18 in this patient.

Transfection of cells from patients with leukocyte adhesion deficiency with an integrin beta subunit (CD18) restores lymphocyte function-associated antigen-1 expression and function

Leukocyte adhesion deficiency (LAD) is an inherited immunodeficiency disease that is characterized by the deficient expression of the leukocyte adhesion glycoproteins lymphocyte function-associated antigen-1 (LFA-1), Mac-1, and p150,95. This loss of expression is attributed to heterogeneous defects in the common beta subunit shared by these glycoproteins. Here we demonstrate that expression of the LFA-1 alpha beta heterodimer in EBV-transformed B lymphoblastoid cells from LAD patients can be recovered after transfection with the beta subunit cDNA contained in an EBV-based vector. Four patients with differing severities of LAD comprising three distinct classes of mutations were studied. Flow cytometry analysis of stably transfected patient cells revealed near normal levels of expression of both the alpha and beta chains of LFA-1, and immunoprecipitation studies confirmed that fully processed alpha and beta chains were being expressed at the cell surface. In addition, Northern analysis of mRNA expression also demonstrated that the transfected LAD patient cells were expressing high quantities of exogenous beta subunit mRNA. Functional studies such as homotypic adhesion and adhesion to a purified counterreceptor for LFA-1, intracellular adhesion molecule-1, demonstrated that LFA-1 function had been restored in the stably transfected LAD patient cell lines. These studies unequivocally show that the defect in cells from patients with LAD is in the leukocyte integrin beta subunit.

Mouse macrophage beta subunit (CD11b) cDNA for the CR3 complement receptor/Mac-1 antigen

The cDNA for the common beta Mac-1 subunit (CD11b) of the mouse LFA-1/Mac-1/p150,95 group of leukocyte cell adhesion receptors, formally designated integrin beta 2, has been cloned and sequenced. Clones were isolated from cDNA libraries made from J774 macrophage and WEHI-3B myelomonocytic tumor cells which express this subunit as a component of the macrophage activation antigen 1 (Mac-1), also known as complement receptor type 3 (CR3). This subunit is expressed as a single, abundant mRNA species approximately 2.7 kilobase (kb) in size. The 2422 base pair (bp) cDNA sequence obtained codes for a 771 amino acid protein organized with leader, extracellular, transmembrane, and cytoplamic domains of 23, 680, 23, and 46 amino acids, respectively, yielding an 82,700 mature protein of 747 amino acids. The mouse beta Mac-1 subunit is highly similar to its human counterpart with an overall sequence identity of 81% and identical positioning of 5 out of 6 potential N-linked glycosylation sites, as well as 56 Cys residues that are organized in repeating motifs characteristic of integrin beta subunits. The most highly conserved regions are the transmembrane and cytoplasmic domains where only 4 out of 69 amino acids differ, indicating that the functions associated with this domain in Mac-1-mediated processes, such as iC3b-triggered phagocytosis, have been evolutionarily conserved.

Regulation of expression of the CD11b and CD18 subunits of the neutrophil adherence receptor during human myeloid differentiation

The receptor on human myeloid cells that mediates cellular adherence consists of a heterodimer complex (designated CD11b/CD18). This receptor complex plays a critical role in leukocyte chemotaxis, adherence to vascular endothelium, and phagocytosis. We investigated expression of the CD11b subunit of this adherence receptor complex in various leukocyte populations. As previously described for the CD18 subunit, enhanced CD11b surface antigen and mRNA expression are present in peripheral blood granulocytes, as well as in chemically induced, differentiating HL-60 cells. However, in contrast to CD18 mRNA expression, which is transcriptionally regulated in differentiating HL-60 cells, the steady state levels of CD11b mRNA appear to be post-transcriptionally regulated in these cells. Thus, although the steady state levels of mRNA for the individual subunits of the CD11b/CD18 adherence receptor complex generally parallel each other during human myeloid differentiation, the mechanisms responsible for regulating these levels are distinctly different.