Biometrical implications of factorial experiments for the study of lymphocyte mitogenic response

Computational models in immunological methods: an historical review

The utilization of computational models in immunology dates from the birth of the science. From the description of antibody-antigen binding to the structural models of receptors, models are utilized to bring fundamental understandings of the processes together with laboratory measurements to uncover implications of these data. In this review, an historical view of the role of computational models in the immunology laboratory is presented, and short mathematical descriptions are given of fundamental assays. In addition, the range of current uses of models is explored -- especially as seen through papers which have appeared in the Journal of Immunological Methods from volume 1 (1971/1972) to volume 208 (1997). Each paper which introduced a new mathematical, statistical, or computer simulation model, or introduced an enhancement to an instrument through a model in those volumes is cited and the type of computational model noted.

The statistical analysis of data from immunoepidemiological studies

Immune responses encountered in human populations display a higher level of heterogeneity than is typically seen with laboratory animals, and the expected clear distinction between responders and non-responders to particular antigens may not be apparent. In such a situation, the methods of statistical analysis traditionally used in laboratory studies may no longer be appropriate, and there is no consensus among immunologists about how such data should be analysed. Using data from a large study of lymphocyte proliferation responses to candidate antigens for a vaccine against Plasmodium falciparum malaria, we discuss questions such as the appropriateness of logarithmic transformation of the data, the use of the stimulation index versus delta--cpm, the use of the proportion of responders for comparing two groups of individuals, and the choice of threshold for defining such a responder.

Mitogen dose-dependent effect of weak pulsed electromagnetic field on lymphocyte blastogenesis

The effects of pulsed extremely low frequency electromagnetic fields on human peripheral blood lymphocyte mitogenesis induced by phytohaemoagglutinin, concanavalin A or calcium ionophore A23187 were studied. The dependence of the field effect on mitogen concentrations was investigated. Field exposure produced strong inhibition of DNA synthesis when optimal doses of mitogens were used, confirming our previous findings. Opposite effects were observed at suboptimal concentration of mitogens. Experiments performed by exposing cell cultures to the field for short periods indicated that a field application of at least 6 h is needed to influence irreversibly lymphocyte blastogenesis.

Effect of age and periodontal disease status in man on the spontaneous proliferation of peripheral blood lymphocytes

Spontaneous lymphocyte proliferation (SLP), as a measure of the autologous mixed-lymphocyte reaction (AMLR), was used to detect possible systemic immunoregulatory differences between periodontally-diseased subjects and age-matched controls. Forty-four subjects formed four groups; young-healthy (YH), young-diseased (YD), old-healthy (OH) and old-diseased (OD) based on clinical examination to assess loss of attachment and bleeding on gentle probing. The mean loss of periodontal attachment for the YD, OH and OD groups was 5.9, 3.3 and 6.0 mm respectively, and the mean bleeding index was 0.39, 0.18 and 0.44. Their SLP was assessed using peripheral-blood mononuclear cells on days 3, 5, 7, 9 and 11 in culture. The peak response for the YH group occurred at day 7; that of the OH group was not until day 9, suggesting that age may alter the kinetics of the reaction as a delay in peak responsiveness. Using log transformation, to reduce individual variations within each group, SPL of peripheral-blood mononuclears from diseased subjects was depressed at day 7 for the young age group (p less than 0.01) and at day 9 for the older group (p less than 0.05). Not all diseased subjects had a depressed response, suggesting that SPL per se may reflect current rather than past disease activity. It seems that SPL could identify particular disease groups provided age and time of peak responsiveness are taken into account.

Optimum cell numbers for mixed lymphocyte responses in hanging-drop microcultures

The conditions required for optimum mixed lymphocyte culture (MLC) responses in hanging-drop (HD) microcultures in Terasaki trays have been investigated. Compared with conventional (200 microliter) MLC, HD-MLC required 5-10 times fewer cells, and 10% of the amount of culture medium and 3H-thymidine label. Peak uptake of label in HD-MLC was mutually responder-stimulator concentration dependent. Differences in response to related and unrelated lymphocytes indicate that HLA-D determinants are detected in HD-MLC.

Antigen specific in vitro activity of lymphocyte subpopulations from Mantoux positive and negative subjects assessed by lymphocyte proliferation assay

A micromethod for the lymphocyte proliferative assay and multifactorial analysis of stimulation indices classified according to subjects, lymphocyte combinations and antigens was used to elucidate deficient Mantoux (Mx) reactions in BCG-vaccinated subjects. It was possible to group each of the factors so that interactions between the two latter factors were not present within but only between groups. Comparisons between the subject groups showed a clear association between results of this in vitro test with PPD antigen and the Mx test carried out with 1 TU. The in vitro test had the advantage of being more sensitive and of not introducing the immune reactions occasionally seen with the Mx test. Thymus-processed lymphocytes were the cells responsible with functions both as effector and regulator cells, B lymphocytes had only regulatory properties.

Effects of pulsed electric fields on mouse spleen lymphocytes in vitro

The effects of pulsed electric fields on cell membranes were investigated. In vitro exposure of mouse splenocytes to a single high-voltage pulse resulted in an increase in membrane permeability that was dependent on both the electric field strength and the pulse duration. Exposure to a 2 microseconds, 3.0 kV/cm pulse resulted in the induction of a 1.26 V transmembrane potential, and elicited a 50% loss of intracellular K+. These results are in agreement with previous studies of the effects of pulsed electric fields on erythrocytes and microorganisms. The effect of pulsed electric fields on the functional integrity of lymphocytes was investigated by measuring [3H]thymidine incorporation by cells cultured in the presence and absence of various mitogens following exposure to an electrical pulse. No statistically significant effects on the response of mouse spleen lymphocytes to concanavalin A, phytohemagglutinin or lipopolysaccharide were observed following exposure to 2 microseconds electric pulses at amplitudes of up to 3.5 kV/cm. Exposure to a single 10 microseconds pulse of 2.4-3.5 kV/cm produced a statistically significant reduction in the response of lymphocytes to lipopolysaccharide stimulation that was attributed to cell death.

Variation in mitogen-induced ovine lymphocyte blastogenesis: adherent cells or 2-mercaptoethanol restore randomly depressed responses

Peripheral blood leucocytes (PBL) isolated 23 times over a 6-week period from four normal sheep showed considerable variation in serially tested responses to predetermined optimal concentrations of concanavalin A (Con A), phytohaemagglutinin (PHA), and pokeweed mitogen (PWM). Con A responses, in particular, varied widely and were often randomly depressed (21 of 91 times compared to 15 of 91 times for PHA or PWM). The addition of as few as 1% adherent cells (AC) to depressed cultures fully restored the PBL proliferative response to normal levels. Addition of greater numbers of AC (5 or 10%) had little further enhancing effect on depressed cultures. The addition of 1, 5, or 10% AC to cultures that were responding at normal levels increased responses only slightly. Autologous or allogeneic AC were equally effective. Addition of 2-mercaptoethanol (2-ME) to depressed cultures only partially restored the blastogenic response to Con A and had little effect on normal cultures.

In vitro evaluation of porcine lymphocyte response to phytohaemagglutinin using a modified "whole blood" technique

The purpose of these investigations was to develop a modified whole blood technique for measuring quantitatively the responsiveness of pig peripheral blood lymphocytes to phytohemagglutinin (PHA) in vitro. Washed blood cells from a fixed volume of blood were suspended in culture medium supplemented with foetal calf serum and stimulated with a pure mitogenic PHA preparation. The stimulation was measured by the incorporation of 3H-thymidine. Data are presented to show the effect of different variables on the culture system. The transformation response was measured at different levels of PHA and the reproducibility of the different responses from repeated investigations was used to evaluate the usefulness of the test. The best reproducibilities of the stimulation response were found at the high PHA concentrations. Also the calculated PHA concentration giving maximum stimulation response had a relatively high reproducibility and indicates that this value is a convenient and reliable alternative measure of the functional capacity of the lymphocytes.

Statistical evaluation of the lymphocyte proliferation assay with non-stimulated cultures

A micromethod for the lymphoproliferative assay has been evaluated statistically with non-stimulated human lymphocyte combinations. Different variance components were estimated by means of a hierarchical analysis of variance. Instead of using an arbitrary value for a significant difference between stimulated and non-stimulated cultures, the value can be calculated on the basis of the components of variance in the experimental design. The method disclosed systematic differences between the values of control cultures depending on the lymphocyte combinations and groups of persons examined, which underlines that every experiment should always contain non-stimulated cultures. Further, cell-cell cooperation and differences in spontaneous DNA synthesis within individual lymphocyte populations could be demonstrated.

Conditions for measuring DNA synthesis in PHA stimulated human lymphocytes in 20 microliters hanging drops with various cell concentrations and periods of culture

We have studied conditions for measuring the uptake of [3H]thymidine ([3H]Tdr) by human lymphocytes in inverted microcultures, varying cell concentrations and periods in culture. Analysis of variance of the log values for [3H]Tdr uptake may be used to separate effects of variables and their interactions. A pulse time of 2 h, a total thymidine concentration of about 1 microgram/ml and a specific activity of [3H]Tdr of 2 Ci/mmole were optimal. Variables such as cell concentration, period of culture, type of serum and dose of PHA were shown to interact, suggesting that these variables should be examined together especially when comparing different samples of lymphocytes. Conditions for doing this simply in small volumes are now available for culturing, thymidine pulsing, harvesting and analysis of data.