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Biomedical subjects

T F Tedder

Publications and source records attributed to T F Tedder.

At least 181 records · Page 10Linked to original sources
PubMed1986

Epstein Barr virus binding induces internalization of the C3d receptor: a novel immunotoxin delivery system.

Epstein Barr virus (EBV) infection of human B lymphocytes is initiated by selective binding of the virus to the C3d receptor (EBV/C3d receptor) on the cell surface and results in polyclonal proliferation of infected cells. In these studies we examined the fate of the EBV/C3d receptor during viral infection by using an immunotoxin made from a monoclonal antibody (HB5) reactive with the receptor and the potent toxin, gelonin. Binding of the HB5-gelonin conjugate to the EBV/C3d receptor before EBV infection (at concentrations as low as 10(-11) M) significantly inhibited the subsequent polyclonal proliferation of virus-infected B lymphocytes. HB5 antibody and gelonin alone did not inhibit proliferation. Because internalization of gelonin-antibody conjugates is required to cause cytotoxicity, these results indicate that infection of B lymphocytes with EBV selectively induced endocytosis of the EBV/C3d receptor with concomitant internalization of the immunotoxin. Proliferation of B lymphocytes that were activated by prior infection with EBV, or activated by cross-linking of their surface immunoglobulin molecules, was not inhibited by the antibody-toxin conjugate even at concentrations as high as 10(-7) M. Also, the growth of B lymphoblastoid cell lines cultured in the presence or absence of infectious EBV was not inhibited by HB5-gelonin. Thus, our results suggest that the EBV/C3d receptor is internalized only during the infection of normal B lymphocytes by EBV, with co-internalization of immunotoxin, and indicate that internalization of the EBV/C3d receptor-immunotoxin complex does not occur simply as a consequence of activation and proliferation of B lymphocytes. The use of a ligand to induce endocytosis of its receptor offers a new strategy for the selective delivery of immunotoxins to cells and may be more generally applicable.

Adult↗
PubMed1986

Antibodies reactive with class II antigens encoded for by the major histocompatibility complex inhibit human B cell activation.

Although class II antigens encoded by genes in the major histocompatibility complex (MHC) are important as recognition structures for immunoregulatory cell interactions, the precise functional role of these molecules in the biological responses of B lymphocytes is unknown. In the studies described here, we have examined the effects of six monoclonal antibodies reactive with human class II MHC antigens on B cell activation and proliferation. Peripheral blood IgM+ B cells purified by fluorescence-activated cell sorter (FACS) techniques were stimulated with anti-mu antibodies, protein A-bearing Staphylococcus aureus (SAC), or in T cell-dependent activation cultures. The B cell proliferative responses induced by these stimuli were inhibited 68 to 90% by low concentrations (1 to 5 micrograms/ml) of antibodies reactive with class II MHC antigens. Antibodies specific for DR and DQ antigens were both effective inhibitors of B cell proliferation. This inhibition was not due to the binding of antibody to B cell Fc-IgG receptors, because IgM and IgG anti-class II antibodies were equally potent as inhibitors. When responses of B cells fractionated on the basis of cell size by forward angle light scatter were analyzed, anti-DR and anti-DQ antibodies inhibited the proliferation of small, resting IgM+ cells induced by T-independent as well as T-dependent stimuli. Activation-dependent increases in B cell size and RNA synthesis were similarly inhibited. In contrast, the responses of large B cells (that had been preactivated in vivo) to T cell-derived B cell growth factors were not affected by anti-class II antibodies. These data suggest that class II MHC molecules do not serve merely as cellular interaction structures but also directly participate in early events of the B cell activation cascade that precede cell enlargement or increased RNA synthesis. After activation and expression of receptors for growth factors, however, B cell class II MHC antigens no longer mediate signals required for mitogenesis.

Adult↗
PubMed1986

Antibodies reactive with the B1 molecule inhibit cell cycle progression but not activation of human B lymphocytes.

The B1 cell surface molecule (CD20) is a 35-kDa phosphoprotein expressed by B lineage cells during most stages of differentiation. Some monoclonal antibodies reactive with B1 induce activation while others, anti-B1a, inhibit B lymphocyte function. To further determine the requirement of B1 molecule function in proliferation and differentiation the effects of anti-B1a antibody binding on early cellular activation events were examined. Immunoglobulin secretion of lymphocyte cultures stimulated with pokeweed mitogen was maximally inhibited if the antibody (1-10 micrograms/ml) was added during the first 24 h of culture. However, even high antibody concentrations were unable to inhibit increases in free intracellular Ca2+ concentrations immediately following cross-linkage of cell surface immunoglobulin, or inhibit cell enlargement and the expression of transferrin and interleukin 2 receptors. Antibody binding to B1 inhibited RNA synthesis (37-80%) and progression through cell cycle following activation. In contrast, proliferation induced by phorbol myristate acetate was not inhibited by antibody binding to the B1 molecule. The findings that the earliest activation events and phorbol myristate acetate-induced proliferation were not inhibited by antibody binding to B1 suggest that inhibition is due to the blocking of a step of the activation process required for cell cycle progression and differentiation, rather than blocking initial signal transduction across the membrane or providing a negative or suppressive signal.

Antibodies, Monoclonal↗
PubMed1986

Function of the LFA-1 and T4 molecules in the direct activation of resting human B lymphocytes by T lymphocytes.

Activated T lymphocytes can provide all of the signals necessary to induce the proliferation of resting B lymphocytes. The activation signal is presumably initiated through direct T-B lymphocyte contact. The role of the leukocyte function antigen-1 (LFA-1) and T4 molecules in the activation of purified, small B lymphocytes by mitomycin C-treated T lymphocytes was examined by using monoclonal antibodies that react with and inhibit the function of these molecules. Anti-LFA-1 antibody binding significantly inhibited T-B lymphocyte interactions that result in B lymphocyte proliferation. In contrast, the presence of anti-T4 antibodies at concentrations as high as 100 micrograms/ml did not inhibit this interaction. These results indicate that the B lymphocyte activation signal may not be mediated through the interaction of T4 molecules with major histocompatibility complex class II antigens of the B lymphocyte but is a cell-cell contact-dependent event that is facilitated by LFA-1 molecules.

Antibodies, Monoclonal↗
PubMed1986

The role of receptors for complement in the induction of polyclonal B-cell proliferation and differentiation.

A panel of monoclonal antibodies and ligands that bind to the CR1 or CR2 complement receptors of B cells has been used to investigate the role of these membrane molecules in regulating B-cell proliferation and differentiation. When CR2 was modulated from the surface of B cells by treatment with the HB-5 antibody and a secondary goat anti-mouse immunoglobulin antibody, Epstein-Barr virus-induced polyclonal B-cell proliferation and immunoglobulin production were inhibited by 83 and 90%, respectively. In contrast, modulation of other cell surface molecules, HB-2, B1, and the C3b receptor (CR1), or pretreatment of B cells with C3d,g (a CR2 ligand) or HB-5 antibody, alone minimally inhibited these responses. Neither the HB-5 antibody C3d,g, nor a monoclonal antibody (YZ-1) reactive with CR1 induced resting B cells to proliferate, nor did they alter anti-mu antibody-induced proliferation. Similarly, treatment with C3d,g or with the HB-5 or YZ-1 antibodies did not induce B cells to secrete immunoglobulin or affect pokeweed mitogen-induced plasma-cell formation. Whereas CR2 appears to be the functionally relevant receptor for Epstein-Barr virus on B cells, the effects of ligand interactions with CR1 and CR2 on normal B-cell proliferation or differentiation remain unidentified.

Adult↗
PubMed1985

Human lymphocyte differentiation antigens HB-10 and HB-11. I. Ontogeny of antigen expression.

T, B, and NK cells appear to represent separate lymphocyte lineages, but indirect evidence suggests that they may be related via a common lymphoid precursor cell. We have produced two monoclonal antibodies, HB-10 (IgM) and HB-11 (IgG1), by fusing spleen cells from mice immunized with the human B cell line SB, and have shown that both antibodies react with lymphocyte-specific cell surface antigens present on T, B, and NK cells, but not on other types of blood cells. The antibodies were reactive with most cell lines and malignancies of B cell origin and with some of T and NK cell lineage. Although the populations of cells expressing these two antigens were virtually identical, the HB-10 and HB-11 antibodies identified separate protease-sensitive determinants on the cell surface. The HB-11 antigenic determinant was also sensitive to neuraminidase and periodate treatments, but the HB-10 determinant was not. Antigen expression by lymphocytes from fetal, newborn, and adult tissues was examined. Within the B cell lineage, these antigens were expressed by most pre-B cells in bone marrow (88% +/- 5) and almost all B cells, but were not expressed by mature plasma cells. Virtually all of the granular lymphocytes in blood marked by the Leu-7 and Leu-11 (anti-Fc receptor) antibodies were HB-10+ and 11+. Among T lineage cells, the HB-10 and 11 antigens were expressed by a subset of relatively mature T3+ thymocytes and by greater than 90% of the T cells in newborn blood. In adults, however, only 65% of blood T cells and 24 to 30% of splenic or tonsillar T cells expressed the HB-10 and HB-11 antigens. The postnatal emergence of T cells which, like plasma cells, do not express these antigens suggests that post-thymic T lymphocyte maturation occurs and may be an activation-dependent process.

Adult↗
PubMed1985

Human lymphocyte differentiation antigens HB-10 and HB-11. II. Differential production of B cell growth and differentiation factors by distinct helper T cell subpopulations.

Two monoclonal antibodies (HB-10 and HB-11), which react with human T, B, and NK cells, identify approximately 50% of the Leu-3+ T helper (TH) cells in adult blood. In the present studies, the functional capabilities of the HB-11+ and HB-11-TH cell subpopulations were examined after purification by fluorescence-activated cell sorting. Both subpopulations proliferated in response to PHA, Con A, PWM, and OKT-3 antibodies. The HB-11+ TH cells gave a minimal proliferative response to soluble tetanus toxoid antigen, whereas HB-11-TH cells responded well. After mitogen activation, both HB-11+ and HB-11-TH cells and to produce soluble factors which induce large B cells to proliferate. However, PWM-stimulated HB-11+TH cells were incapable of inducing B cells to differentiate into antibody-secreting plasma cells, whereas HB-11-TH cells were efficient in this regard. The results suggest that the HB-11 antigen is expressed on a subpopulation of virgin TH cells that can produce B cell growth factors but are deficient in the ability to produce B cell differentiation factors.

Antibodies, Monoclonal↗
PubMed1985

Evaluation of lymphocyte differentiation in primary and secondary immunodeficiency diseases.

The differentiation status of T and B cells was evaluated in patients with common variable immunodeficiency (CVI), selective IgA deficiency (IgA), X-linked agammaglobulinemia (XLA), and the acquired immune deficiency syndrome (AIDS) with the use of conventional lymphocyte markers and four new monoclonal antibodies that identify lymphocyte subpopulations. These antibodies are HB 4, which identifies a subpopulation of resting B cells; HB 5, which identifies the C3d/EBV receptor on mature B cells; HB 7, which identifies immature B lymphocytes; and HB 10, which reacts with virgin but not activated or memory T cells. T and B cells from the IgA patients typically had normal phenotypic profiles, whereas diverse patterns of lymphocyte maturation were observed in CVI. In 11 of 16 CVI patients, B cells had normal antigenic phenotypes. Although B cells from four other CVI patients had normal frequencies of HB 5 and HB 7 antigen expression, few expressed the HB 4 antigen, suggesting that they were activated. In contrast, a large percentage of B cells from one CVI patient were of an immature phenotype. The expression of the HB 10 antigen by T cells in CVI patients was also variable, being normal in 10 of 16 patients, yet significantly decreased in six others. The vast majority of the limited numbers of IgM B cells from five XLA patients (greater than 100-fold reduction) has an immature phenotype (HB 4-5-7+). Interestingly, the circulating T cells in XLA patients were phenotypically similar to those in normal newborns, suggesting that T cell immaturity or defective T cell activation may occur in these B cell-deficient individuals. Circulating B cells from AIDS patients were mostly HB 7-, with variable expression of the HB 4 antigen and significantly decreased expression of the HB 5 antigen. Most of the T cells from AIDS patients were HB 10-, and thus appeared to be activated.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Development and distribution of a human B cell subpopulation identified by the HB-4 monoclonal antibody.

Monoclonal antibodies have been successfully used to identify B cell differentiation antigens, few of which mark discrete B cell subpopulations. We have produced a monoclonal antibody, HB-4, against a cell surface antigen on the human B cell line, BJAB, which has an unusual distribution on normal lymphoid cells. HB-4, an IgM antibody, was found to react with an antigen that is expressed by a subpopulation of B cells, approximately 50% of natural killer cells, and not by other types of cells in bone marrow, blood, and lymphoid tissues. In two-color immunofluorescence assays, the HB-4-reactive antigen was found on less than 5% of immature IgM+ B cells in fetal liver and bone marrow and on 25% of B cells in fetal spleen. The HB-4 antibody reacted with 40% of IgM+ cells in newborn blood and 60% of B cells in adult blood. In contrast, only 2 to 26% of IgM+ B cells in the peripheral lymphoid tissues of adults were HB-4+. HB-4+ B cells could be induced to proliferate by cross-linkage of their surface immunoglobulins but not by T cell-derived growth factors. The subpopulation of activated B cells that is responsive to T cell-derived differentiation factors was HB-4-, as were plasma cells. The HB-4 antibody was reactive with some but not all B cell malignancies and cell lines, and not with malignancies or cell lines of other lineages. The HB-4 antigen may therefore serve as a useful nonimmunoglobulin marker for the identification of a subpopulation of mature resting B cells that are present in the highest frequency in the circulation.

Adult↗
PubMed1985

The B cell surface molecule B1 is functionally linked with B cell activation and differentiation.

The B1 molecule is a 32,000 m.w. phosphorylated cell surface protein expressed exclusively by B cells from the mid pre-B until the plasma cell stage of differentiation. Two monoclonal antibodies (gamma 2a and mu) reactive with this molecule were used to assess the role of B1 in B cell activation, proliferation, and differentiation. The anti-B1 antibodies at concentrations ranging from 0.1 to 100 micrograms/ml significantly inhibited B cell proliferation induced by anti-mu antibodies, Staphylococcus aureus Cowan strain 1, activated T cells, and Epstein Barr virus. Although capable of inhibiting proliferation, anti-B1 antibody in soluble form or coupled to beads did not activate B cells or induce proliferation. Antibodies of comparable isotypes or against other B cell-restricted antigens, including B2, B4, B5, and HB-5, did not inhibit activation. Pretreatment of B cells with anti-B1 antibody did not inhibit activation, indicating that B cells had to be cultured with anti-B1 antibody for anti-B1-mediated inhibition to occur. Maximum inhibition was obtained when anti-B1 antibody was added at the initiation of culture. In agreement with this, growth factor-dependent proliferation of preactivated B cells was not inhibited by anti-B1 antibodies. Comparable inhibition of B cell activation was noted with antibodies reactive with class II antigens of the major histocompatibility complex with the exception that anti-B1 antibody inhibited immunoglobulin secretion in pokeweed mitogen assays, whereas anti-DR antibody did not. These results suggest that the B1 molecule may serve a central role in the regulation of B cell activation and differentiation.

Adult↗
PubMed1984

Epstein-Barr virus receptor of human B lymphocytes is the C3d receptor CR2.

Identity of the Epstein-Barr virus (EBV) receptor with the complement receptor type 2 (CR2) was established in three sets of experiments using the monoclonal antibodies, HB-5 and anti-B2, which recognize a Mr 145,000 B-lymphocyte membrane protein that is CR2. First, the rank order for binding of fluoresceinated EBV to four lymphoblastoid cell lines (SB, JY, Raji, and Molt-4) was identical to the rank order for binding of HB-5 and anti-B2 by analytical flow cytometry. Second, pretreatment of cells with HB-5 followed by treatment with goat F(ab')2 fragments to mouse IgG blocked binding of fluoresceinated EBV on SB, a B-lymphoblastoid cell line. Virus attachment was not inhibited by HB-5 alone, second antibody alone, rabbit anti-C3b receptor, or UPC10 (an irrelevant monoclonal antibody). Third, transfer of CR2 from SB to protein A-bearing Staphylococcus aureus particles, to which HB-5 had been absorbed, conferred on them the specific ability to bind 125I-labeled EBV. We conclude that CR2 is the EBV receptor of human B lymphocytes.

Antibodies, Monoclonal↗
PubMed1984

Identification of a 145,000 Mr membrane protein as the C3d receptor (CR2) of human B lymphocytes.

The C3d receptor (CR2) of human B lymphocytes mediates the binding to these cells of immune complexes that have activated the complement system and bear the fragments of C3, iC3b, C3d,g, and C3d. A 145,000 Mr membrane protein previously described as being recognized by the monoclonal antibody HB-5 and shown to be expressed only by B lymphocytes and B lymphoblastoid cell lines, such as Raji, was assessed for its possible identity as CR2. Treatment of Raji cells with HB-5 and goat F(ab')2 anti-mouse IgG (GaM) diminished the capacity of these cells to form rosettes with sheep erythrocyte (E) intermediates bearing 130,000 molecules of iC3b or C3d, whereas treatment with the monoclonal antibody alone had no effect. The capacity of peripheral blood B lymphocytes to bind EC3d was similarly inhibited by the combination of HB-5 and GaM. The possibility that HB-5 may interact with a site on CR2 that is distinct from the ligand binding site permitted the direct analysis of the capacity of the HB-5 antigen to bind to the C3 fragments. Protein A-containing Staphylococcus aureus particles to which HB-5 had been bound were incubated with detergent lysates of Raji cells and B lymphocytes under conditions that had been shown to be associated only with the binding of the 145,000 Mr antigen. These particles bearing HB-5 and antigen derived from either cell type were shown to adhere specifically to EiC3b and EC3d, demonstrating that transfer of the HB-5 antigen from CR2-bearing cells to S. aureus particles led to the acquisition of CR2 function by the particles. The additional findings that the relatively weak capacity of Raji cells to form rosettes with EC3b was inhibited by HB-5 and that the S. aureus particles bearing immunoadsorbed HB-5 antigen bound to EC3b indicated that the C3b-binding function of the CR1-negative Raji cell resides in CR2, rather than in other membrane proteins.

B-Lymphocytes↗
PubMed1984

Discontinuous expression of a membrane antigen (HB-7) during B lymphocyte differentiation.

We have examined the expression of a cell surface antigen by B lineage cells in human fetuses, newborns and adults using a newly produced monoclonal antibody, HB-7. The HB-7 antigen was found to be a protease sensitive 45,000 MW molecule that appeared to be the same molecule recognized by the OKT-10 antibody. The HB-7 reactive molecule was expressed by all fetal pre-B and B cells, and 50% of newborn blood and adult bone marrow B cells. In contrast, only a small minority of B cells (2-12%) from blood, spleen and tonsil of adults were weakly HB-7+. The pokeweed mitogen-responsive B cell precursors of plasma cells were also HB-7-, but the HB-7 antigen was re-expressed during the plasma cell stage. We conclude that this antigen is unique among known B cell differentiation antigens in its intermittent pattern of expression during B cell development. The reactivity of the HB-7 antibody with immature, but not mature, B cells makes it well suited for studies of B cell ontogeny.

Antibodies, Monoclonal↗
PubMed1984

Expression of C3d receptors during human B cell differentiation: immunofluorescence analysis with the HB-5 monoclonal antibody.

We have examined human B lymphocytes at different stages of differentiation for the expression of surface receptors for the C3d fragment of complement. C3d receptors (C3dR) were identified by indirect immunofluorescence using the HB-5 monoclonal antibody, which recognizes a 145,000 m.w. C3dR molecule on B lymphocytes. Pre-B and immature B cells from fetal bone marrow and liver did not express C3dR, whereas a small subpopulation (25%) of B cells in fetal spleen were C3dR+. Approximately 50% of the B cells in adult bone marrow were C3dR+, whereas the more mature B cells in the blood of newborns and adults and in peripheral lymphoid tissue of adults uniformly expressed the C3dR. Activated B cells responsive to T cell-derived differentiation factors were C3dR+, whereas plasma cells rarely expressed C3dR. T cells, NK cells, erythrocytes, and myelomonocytic cells did not express detectable surface C3dR. These results suggest that in hematopoietic and lymphoid tissues, the expression of C3dR is a specific feature of relatively mature lymphoid cells of B lineage.

Adult↗
PubMed1983

Expression of C3b receptors on human be cells and myelomonocytic cells but not natural killer cells.

We have examined natural killer (NK) cells, B cells and myelomonocytic cells at different stages of differentiation for the expression of surface C3b receptors (C3bR). Receptor presence was detected using affinity-purified F(ab')2 anti-C3bR antibodies in indirect immunofluorescence assays. NK cells, identified in fetal and adult tissues by the monoclonal antibody HNK-1, were C3bR- except for infrequent C3bR+ HNK-1+ cells in some blood samples. NK cells were not induced to express C3bR by exposure to interferon, target cells, or phorbol myristate acetate. B cells gradually acquired the ability to express C3bR with maturity: 15% of large pre-B cells were C3bR+, 35 to 48% of small pre-B, 60 to 80% of immature B, and 99% of mature B cells. Mature plasma cells were rarely C3bR+. Myelomonocytic cells acquire C3bR relatively late during their development, with neutrophils beginning to express C3bR during the band stage of differentiation. All adult blood myelomonocytic lineage cells, identified by the monoclonal antibody MMA and by morphology, were C3bR+.

Animals↗
PubMed1983

Characterization of human T lymphocytes that express the C3b receptor.

The presence of the C3b receptor (C3bR) on human peripheral blood T lymphocytes was recognized by the capacity of rabbit F(ab')2 anti-C3bR and tetramethylrhodamine isothiocyanate (TRITC)-conjugated goat F(ab')2 anti-rabbit F(ab')2 to stain 14.5 +/- 3.7% (mean +/- SEM; n = 5) of lymphocytes forming rosettes with sheep erythrocytes (E). The F(ab')2 anti-C3bR also blocked the capacity of peripheral blood lymphocytes stained with OKT11 to form rosettes with bovine E bearing C3b and immunoprecipitated a single membrane protein having a m.w. of approximately 250,000 from detergent lysates of 125I-labeled, purified T cells. Measurement by fluorescent flow cytometry of the quantitative expression of the C3bR indicated that T cells had slightly more antigenic sites/cell than did E and approximately 10-fold fewer sites than were present on B cells. The surface constituents of the peripheral blood T cells expressing the C3bR were assessed in an assay that employed simultaneously three markers: rosette formation with sheep E, TRITC staining with anti-C3bR and fluorescein isothiocyanate (FITC)-staining with a panel of monoclonal antibodies or with aggregated IgG. Among lymphocytes forming rosettes with sheep E and expressing the C3bR, 99.6 +/- 0.4%, 65.0 +/- 5.8%, 17.2 +/- 6.2%, and 15.3 +/- 5.0% of the cells expressed antigens detected by OKT3, OKT4, OKT8, and OKM1 monoclonal antibodies, respectively. Ninety-seven per cent of the C3bR-bearing T cells were also capable of specifically binding aggregated IgG, indicating the presence of Fc receptors for IgG (Fc gamma R) on these cells. The T cells expressing the C3bR had large nuclei, thin rims of basophilic cytoplasm and no azurophilic granules. Thus, the C3bR is present on some T cells, all of which have a typical lymphocyte morphology, the T3 antigen and the Fc gamma R.

Animals↗
PubMed1982

Unsaturated fatty acid requirement in Escherichia coli: mechanism of palmitate-induced inhibition of growth of strain WN1.

The minimum requirement for unsaturated fatty acids was investigated in E. coli using a mutant impaired in the synthesis of vaccenic acid. Exogenously supplied palmitic acid was incorporated by this mutant which led to a reduction in the proportion of cellular unsaturated fatty acids. Growth was impaired as the level of saturated fatty acids approached 76% at 37 degree C and 60% at 30 degree C. The basis of this growth inhibition was investigated. Most transport systems and enzymes examined remained active in palmitate-grown cells although the specific activities of glutamate uptake and succinic dehydrogenase were depressed 50%. Fluorescent probes of membrane organization indicated that fluidity decreased with palmitate incorporation. Temperature scans with parinaric acid indicated that rigid lipid domains exist in palmitate-grown cells at their respective growth temperature. Freeze-fracture electron microscopy confirmed the presence of phase separations (particle-free areas) in palmitate-grown cells held at their growth temperature prior to quenching. The extent of this separation into particle-free and particle-enriched domains was equivalent to that induced by a shift to 0 degree C in control cells. The incorporation of palmitate increased nucleotide leakage over threefold. The cytoplasmic enzyme beta-galactosidase was released into the surrounding medium as the concentration of unsaturated fatty acid approached the minimum for a particular growth temperature. Lysis was observed as a decrease in turbidity when cells which had been grown with palmitate were shifted a lower growth temperature. From these results we propose that leakage and partial lysis are the major factors contributing to the apparent decrease in growth rate caused by the excessive incorporation of palmitate. Further, we propose that membrane integrity may determine the minimum requirement for unsaturated fatty acids in E. coli rather than a specific effect on membrane transport and/or membrane-bound enzymes.

Biological Transport, Active↗