Serum factors affecting the incorporation of (3H)uridine by lymphocytes stimulated by concanavalin A. Studies of the role of complement

Metabolic optimization of adoptive T cell transfer cancer immunotherapy: A historical overview

After prolonged extracorporeal multiplication in physiological culture media, there can be curative infusions of a cancer patient's own cytotoxic T cells (adoptive T cell transfer; ACT), which must achieve efficient activation in potentially adverse tumour microenvironments. With spectacular, yet irregular, success, improvements are needed. Developing lymphoid cells are biologically selected, not only for 'near-self' reactivity (positive selection), but also to avoid self-reactivity (negative selection). Thus, success requires harnessing near-self cells while avoiding extreme autoimmune phenomena. Abrupt metabolic changes accompanying T cell activation to leave the G₀ stage and enter the G₁ stage of the cell cycle (eg enhanced glycolysis) are accompanied by increased transcription of the G0S9 gene that mediates salvage synthesis of NAD⁺ from nicotinamide; the latter has recently been shown to increase the efficiency of ACT. Despite theoretical and experimental advances, there has not been parallel progress in simulating in vivo conditions with culture media that were initially formulated for their positive benefits for tumour cell lines (cell survival and proliferation). Yet for lymphoid cells, inhibition or death (ie immunological tolerance) is as important as their activation and proliferation (immunological response). Thus, use of media optimized for the latter may mask the former. The resilience of established culture protocols may have been partly politically driven. However, unphysiological conditions have sometimes yielded fortuitous insights. Optimization of culture media for specific tissues must consider the nature of problems addressed in research settings and the need to avoid mishaps in clinical settings.

Almroth Wright, opsonins, innate immunity and the lectin pathway of complement activation: a historical perspective

Two clinical tests - the erythrocyte sedimentation rate and the opsonic index - have long been known to non-specifically detect pathology based on their responsiveness to changes in serum proteins. In infections serum levels of specific antibodies increase. However, for healthy subjects Wright held that antibodies contributed minimally to opsonic activity (the complement-enhanced phagocytosis of microorganisms). The activity was present in newborn serum, was increased in the acute phase of an immune response prior to antibody increase, and was less specific. Furthermore, defective opsonization was associated with undue susceptibility to certain infections, for which a genetic basis was later found. With the demonstrations of complement-mediated lysis both of normal cells by foreign (plant) lectins, and of foreign cells (microorganisms) by animal lectins, it now appears that endogenous lectins correspond to the heat-stable component of Wright's serum opsonic activity. His work leads to the lectin pathway of complement activation with specificities limited to the recognition of relatively immutable surface sugars - predictable pathogen characters that contrast with the less predictable targets of the adaptive immune system.

Lymphocyte repertoire selection and intracellular self/non-self-discrimination: historical overview

Immunological self/non-self-discrimination is conventionally seen as an extracellular event, involving interactions been receptors on T cells pre-educated to discriminate and peptides bound to major histocompatibility complex proteins (pMHCs). Mechanisms by which non-self peptides might first be sorted intracellularly to distinguish them from the vast excess of self-peptides have long been called for. Recent demonstrations of endogenous peptide-specific clustering of pMHCs on membrane rafts are indicative of intracellular enrichment before surface display. The clustering could follow the specific aggregation of a foreign protein that exceeded its solubility limit in the crowded intracellular environment. Predominantly entropy-driven, this homoaggregation would colocalize identical peptides, thus facilitating their collective presentation. Concentrations of self-proteins are fine-tuned over evolutionary time to avoid this. Disparate observations, such as pyrexia and female susceptibility to autoimmune disease, can be explained in terms of the need to cosegregate cognate pMHC complexes internally before extracellular display.

Sequence analysis and expression in cultured lymphocytes of the human FOSB gene (G0S3)

G0S3 is a member of a set of putative G0/G1 switch regulatory genes (G0S genes) selected by screening cDNA libraries prepared from human blood mononuclear cells cultured for 2 hr with lectin and cycloheximide. The sequence shows high homology with the murine FOSB gene, which encodes a component of the AP1 transcriptional regulator. Comparison of cDNA and genomic sequences reveals a 4-exon structure characteristic of the FOS family of genes. Freshly isolated cells show high levels of FOSB/G0S3 and FOS/G0S7 mRNAs, which decline rapidly during incubation in culture medium. The kinetics of expression suggest that the high initial levels are caused by the isolation procedure, and do not reflect constitutive expression. In cells preincubated for a day, levels of FOS mRNA reach a maximum 20 min after the addition of lectin and decline to control levels over the next 3 hr. Levels of FOSB mRNA reach a maximum 40 min after the addition of lectin and decline to control levels over the next 6 hr. In freshly isolated cells, both FOS and FOSB mRNAs increase dramatically in response to the protein synthesis inhibitor cycloheximide. In preincubated cells, the cycloheximide response is decreased, especially in the case of FOSB. These differences in expression of FOS and FOSB suggest different roles and regulation. Regions of low base order-dependent stem-loop potential in the region of the gene are defined. These indicate where base order has been adapted for purposes other than stem-loop stability (e.g., encoding proteins or gene regulation). Regions of low potential in a 68.5-kb genomic segment containing the FOSB gene suggest that the potential may help locate genes in uncharted DNA sequences.

A "stealth" approach to inhibition of lymphocyte activation by oligonucleotide complementary to the putative G0/G1 switch regulatory gene G0S30/EGR1/NGFI-A

The putative G0/G1 switch regulatory gene G0S30/EGR1/NFGI-A show increased expression shortly after adding concanavalin-A (ConA) to cultured T lymphocytes. However, it is reported that lymphocytes from mice in which the gene has been deleted proliferate normally in response to ConA. This suggests that G0S30 expression is not critical for the response. Paradoxically, others report that proliferation of ConA-stimulated rat lymphocytes is inhibited by an antisense oligonucleotide complementary to G0S30. Because the G0S30 sequence is highly conserved between species, we used a similar oligonucleotide (differing by 1 base) to show for humans that the response to ConA is also inhibited. However, no oligonucleotide-induced changes in the concentrations of G0S30 protein or mRNA are detectable. This suggests that the oligonucleotide is not acting by influencing the expression of G0S30, and may be targeting another gene. The phosphorothioated oligonucleotide was maximally inhibitory at a 50 nM concentration, which is near to the "physiological" concentration found with CpG-containing oligonucleotides to activate mouse B lymphocytes. In the present work, increasing the concentration above 50 nM, or adding further quantities of control oligonucleotides, decreased the inhibition. It is suggested that by using low oligonucleotide concentrations (the "stealth" approach), one may avoid "tripping" an endogenous defense system directed against exogenous oligonucleotides, yet still get sufficient uptake to inhibit lymphocyte activation.

Helper function of rat spleen cells reactive with guinea pig serum

Treatment of rat spleen cells with normal guinea pig serum (GPS) has been shown to produce a significant loss of responsiveness to stimulation with either Con A or PHA. This phenomenon was seen even when the spleen cells were triggered with mitogens up to 96 hr after treatment with GPS, suggesting that GPS had produced a long-lasting alteration in some cells or removed a cell subpopulation. Glass-wool non-adherent spleen cells, known to produce greater responses that unfractionated spleen cells, also had their responses to Con A and PHA reduced by GPS treatment though the response was still greater than that of untreated, unfractionated cells, suggesting that the actual responder cells had been spared by GPS. Suppressor cells did not appear to be the target of GPS because such an effect would have resulted in increased responsiveness and the opposite result was obtained. That a helper cell was affected by GPS was suggested by the following observations: a) the virtually unresponsive GPS-treated spleen cells produced greater than normal responses after removal of glass-wool-adherent suppressor cells; b) the response of glass-wool-nonadherent spleen cells was significantly decreased after GPS treatment; and c) mixtures containing equal numbers of glass-wool-nonadherent and GPS-treated spleen cells also showed reduced responsiveness after GPS treatment.

Role of serum in inhibition of cultured lymphocytes by lysophosphatidylcholine

Serum was heated at various temperatures to inactivate components which might be involved in the regulation of lysophosphatidylcholine (lysoPC) levels in rabbit lymph-node cell cultures. Cells cultured in medium containing serum preheated for 20 min at 66 degrees C ("66 degrees C-serum") were inhibited much more by exogenous lysoPC (5 microM) than were cells cultured in medium containing control serum ("38 degrees C-serum"). This was observed over a 20 h culture period as a slow increase in inhibition of cell labelling with [3H] uridine, which reflected cytotoxic cell damage. Heating serum at 66 degrees C caused (i) conversion of monomeric albumin to highly polymeric forms which were deficient in lysoPC-binding activity, (ii) transfer of lysoPC from albumin to lipoproteins, predominantly high density lipoproteins, and (iii) inhibition of two lysoPC metabolizing activities (which were detected only at low levels in control serum). Addition of albumin to cultures containing 66 degrees C-serum decreased the toxicity of lysoPC to the same extent as did the addition of control serum with an equivalent albumin content. Thus, albumin was the major heat-labile factor protecting cells against lysoPC. However, cell inhibition by lysoPC was dependent on the sequence of heating serum and lysoPC addition. Inhibition was small when lysoPC was added before heating the serum. This could not be explained by a detectable difference in the binding of lysoPC to serum components. Furthermore, although radioactive labelling of cells with [14C] lysoPC was increased in 66 degrees C-serum, this did not correlate with cell inhibition. Increased labelling with [14C] lysoPC occurred several hours before significant cell inhibition was evident and was not affected by the sequence of heating and lysoPC addition. Since preincubation of lysoPC with 66 degrees C-serum increased the inhibition, it is suggested that the heated serum lysoPC generates another factor which is responsible for the cytotoxic effects observed.

The cells involved in cell-mediated and transplantation immunity in the rabbit. XII. The establishment of the optimum conditions for the demonstration of a consistent response for the circulating white blood cells in the mixed leukocyte reaction

Rabbit circulating leukocytes (WBC) have been shown to respond consistently in the allogeneic one-way mixed leukocyte culture reaction (MLR). Culture of the cells for 5--6 days in 5% CO2 in air in medium RPMI 1640 supplemented with normal decomplemented rabbit serum to a concentration of 2.5% provided conditions for an optimal MLR response. The WBC of the majority of the normal rabbits tested (82%) responded in the MLR, in contrast to the negative findings of other investigators. The WBC of a minority of the normal rabbits (18%) did not respond in the conventional MLR; however, the spleen cells of these rabbits consistently responded in the MLR, demonstrating that these rabbits possessed MLR responsive cells which may not have been present in the circulation at the time of analysis. Furthermore, the WBC of the 'non-responder' rabbits responded well in the MLR when the allogeneic WBC stimulator cells were replaced by allogenic spleen cells, suggesting that the WBC responder cells require a helper cell provided by the splenic stimulator cells to facilitate the blastogenic response. Whether the MLR responsive cell in the rabbit is a T cell or a 'T-like' cell with B cell properties has still not been resolved.

Role of complement in the toxicity of dietary legumes

On the basis of in vivo data Jayne-Williams (1) has proposed that the toxicity of dietary legumes is due to their content of lectins which are immunosuppressive. On the basis of in vitro data with cultured lymphocytes (2), it is now proposed that ingested lectins bind to cell surfaces and cause autologous complement components to bind to and destroy immunologically competent cells. The hypothesis throws a possible light on the aetiology of favism and Whipple's disease.

Age-related changes in ConA- and LPS-induced lymphocyte transformation. I. Effect of culture conditions on mitogen responses of blood and spleen lymphocytes from young and aged rats

Age-related changes in LPS- and ConA-responsiveness of rat spleen lymphocytes as judged by 14C-TdR incorporation were studied. It was found that responses to both mitogens decreased with advancing age. This report shows that the reduced 14C-TdR incorporation could not be attributed to decreased cell survival or viability of spleen lymphocytes from old rats, to delayed proliferation of the old lymphocytes, or to differences in minimum mitogen doses required for optimal stimulation. The results suggest that the observed decrease is due to a decrease in the number of mitogen responsive cells. The response to LPS was even more depressed than was the response to ConA. The response to ConA in whole blood is also shown to decline with ageing at multiple mitogen doses.

Further implications of a theory of immunity

The normal intraoperative sonographic features of the spinal canal, spinal cord, conus medullaris, and cauda equina are described and illustrated. Important observations concerning the normal spinal cord include its highly reflective dorsal and ventral surfaces, its uniform hypoechogenicity, and the presence of a central echo. Other easily identified structures within the spinal canal include the dura-arachnoid layer, subarachnoid space, denticulate ligament, dorsal arachnoid septations, and the roots of the cauda equina. In addition the sonographic appearance of commonly encountered iatrogenically introduced material including Gelfoam, Pantopaque, cottonoid pledgets, suture material, Harrington rods, and freeze-dried dura is also demonstrated. These normal images can serve as a baseline for the interpretation of various pathologic conditions of the spinal canal and its contents as seen with intraoperative spinal sonography.

Serum factors affecting the incorporation of (3H)thymidine by lymphocytes stimulated by antigen. I. Serum concentration

Lymph node cells from immunized rabbits were cultured with varying concentrations of antigen in preheated (56°, 30 minutes) autologous serum which had been collected before immunization. [³H]Thymidine was present for the last 6 hours of the 24-hour culture period and the radioactive labelling of acid-precipitable material was then determined.

Changes in labelling due to variations of culture conditions were interpreted according to whether they were specific for control or antigen-treated cultures or non-specific. Cell concentration and serum concentration were predominantly non-specific variables influencing the labelling in control and antigen-treated cultures to a proportionate extent. However, at serum concentrations below 5 per cent labelling was disproportionately inhibited in antigen-treated cultures; there were further minor disproportionate inhibitions at higher serum concentrations.

Labelling was inhibited by increasing the concentration of serum from 25 to 50 per cent, mainly due to a non-diffusible competitive inhibitory activity. Isotope-dilution analysis of the effects of serum on labelling over a wide range of serum concentrations indicated that the relationship was a complex one with at least three step-wise stimulations of the maximum labelling rate being produced by increasing the serum concentrations from 0 to 25 per cent. Labelling in antigen-treated cultures containing post-immunization serum was less than labelling in cultures containing an equal volume of preimmunization serum, but labelling in control cultures was enhanced by post-immunization serum.

These results are shown to be compatible with the proposals (i) that labelling in control cultures reflects the response of cells to low concentrations of endogenous antigens, and (ii) that preimmunization serum and post-immunization serum contain `natural' and `acquired' antibodies respectively, which normally buffer cell-borne receptor sites against reaction with endogenous and exogenous antigens.

Serum factors affecting the incorporation of (3H)thymidine by lymphocytes stimulated by antigen. II. Evidence for a role of complement from studies with heated serum

Lymph node cells from preimmunized rabbits were cultured with varying concentrations of antigen in autologous serum which had been collected before immunization. [³H]Thymidine was added after 18 hours of culture and the cells were harvested at 24 or 66 hours for the determination of the radioactive labelling of acid-precipitable material.

Preheating serum (56°, 20 minutes) enhanced labelling in both control and antigen-treated cultures. This `heat effect' had an early (24 hour) non-specific component, independent of antigen concentration, and a late (66 hour) specific component which was most evident at high antigen concentrations. The conditions of preheating serum (temperature and time) required to produce the heat effect were similar to those required to remove haemolytic activity against rat erythrocytes. However, at certain temperatures and times there were discrepancies. These discrepancies, and data from experiments in which preheated and unheated sera were mixed in varying proportions, or interchanged in different sequences, were explicable on the basis of (i) a requirement for complement in stoichiometric quantities dependent on the number of cells being inhibited, (ii) the involvement of the majority of the cultured cells in the early non-specific component of the heat effect, but only cells capable of proliferating in response to added antigen in the late specific component, (iii) the secretion of complement by cultured cells.

Preheating serum (66°, 20 minutes) depressed labelling in control and antigen-treated cultures and reduced agglutinating activity against both autologous and heterologous erythrocytes.

The results are discussed in relationship to models which require that the size of a specific lymphocyte clone be positively or negatively regulated by the concentration of antigen specific for that clone. With increasing antigen concentration three effects on cells bearing specific receptor sites are distinguished. (i) Cell stimulation under conditions of antigen concentration and cell receptor specificity such that only a few antigen molecules can bind to cells. (ii) Complement-dependent inhibition under conditions such that more antigen molecules can bind to cells. (iii) Complement-independent inhibition under conditions, possibly unphysiological, such that very large quantities of antigen molecules can bind to cells.

Serum factors affecting the incorporation of (3H)thymidine by lymphocytes stimulated by antigen. 3. Evidence for a role of complement from studies with specific complement inhibitors

To obtain further evidence that complement is involved in both the early, non-specific and the late, specific, components of the heat effect (Forsdyke, 1973b), lymph node cells from preimmunized rabbits were cultured with varying concentrations of antigen in autologous preimmunization serum treated with one of three specific complement inhibitors, inulin, Zymosan or cobra venom factor. The Zymosan particles were removed before use of the serum in cultures, but the other inhibitors were not removed.

Inulin only slowly removed haemolytic activity from serum and enhanced the late response to high concentrations of specific antigen. The inulin concentrations required to remove haemolytic activity were similar to those required to enhance the response to antigen. Zymosan-pretreated serum enhanced labelling with [³H]thymidine in both control and antigen-treated cultures to a proportionate extent. No late specific enhancement of labelling was detected, probably because of the secretion of complement by cultured cells. The interpretation of data obtained when Zymosan was left in cultures was complicated by Zymosan acting as an antigen and inducing a primary response to itself. Cobra venom factor reduced the labelling of both control and antigen-treated cultures so that the non-specific component of the heat effect was not detectable. However, the response to high concentrations of specific antigen was enhanced.

It is concluded that although each complement inhibitor shows unique individual characteristics in the system, on balance the results support the view that the activity responsible for both components of the heat effect is complement.