M. Jílek

The relation between the bactericidal activity of complement and the character of the bacterial surfaces

The bactericidal activity of sera not containing antibodies (sera from precolostral piglets and calves) was tested with strains of gram-negative bacteria with different surfaces. The accuracy of the method of bactericidal test was evaluated statistically the bactericidal unit of complement was defined for comparing the activity of sera of different animals and different species. Various methods used for estimating the character of bacterial surface were compared.It was found that the bactericidal activity of piglet sera is directly dependent on the content of complement in the sera tested and the character of the bacterial surface (in the R-form). In selected strains there is a correlation in all criteria characterizing the surfaces of bacteria, and their susceptibility to bactericidal activity of sera; in a group of 37 strains selected at random, correlation with only one of the surface characteristics (stability in solution after heating to 100°C for 1 hour) was found.In calf sera a component was found which increases the effect of complement to some strains (e.g.Shigella shigae). This component may by absorbed from the serum only in the presence of complement. The nature of this factor is discussed.AbstractИзучалось бактерицидное действие сывороток, не содержащих антител (сывороток от преколостральных поросят и телят, еще не получавших молозива), на штаммы грамотрицательных бактерий с различным характером поверхности. Точность методики пробы бактерицидности определяли статистическим методом. Для сравнения эффективности сывороток различных животных и различных видов была определена единица бактерицидности комплемента. Сравнивались различные методы определения характера поверхности бактерий.Было установлено, что существует прямая зависимость между бактерицидным действием сывороток поросят и содержанием комплемента в этих сыворотках и характером поверхности микробов (Я-фазой). У избранных штаммов имеет место корреляция со всеми показателями, характеризующими поверхность микробов и чувствительностью этих микробав к бактерицидному действию сывороток; у случайно подобранной группы 37 штаммов имела место корреляция только с одним показателем (стабильность бакт. суспензии после прогревания в течение часа при 100°C).В телячьих сыворотках был обнаружен компонент, который усиливает действие комплемента на некоторые штаммы (напр., Shigella shigae). Этот компонент можно извлечь из сыворотки истощением только в присутствии комплемента. —Обсуждается характер этого фактора.

The probability of contact between the immunocompetent cell and antigen

The present work is an attempt to make a mathematical formulation of the first part of a well-known hypothesis (Šterzl, 1967) dealing with the course of differentiation of an immunocompetent cell into an antibody-producing cell, namely with the early event—the contact between the cell and antigen. The probability of an event, namely that during the given time interval the contact between the immunocompetent cell and antigen will take place, was studied. The corresponding probability distribution depends substantially on the function describing the fate of antigen following its injection into the organism and further, on the amount of active antigen that is present in the organism in dependence on the length of time after the antigen injection. In addition to a general formula, formula were even obtained describing one particular important function of the decrease in the amount of antigen (exponential).

The number of immunologically activated cells after repeated immunization (A mathematical model)

Using a mathematical model, the effect of the dose of antigen and of the rate of its elimination on the number of immunologically activated cells, derived from a single immunocompetent cell, that are prepared for the change into antibody-producing cells under the condition that further antigenic stimulus takes place, was studied. The following results were obtained under certain assumptions that are explained and discussed in our present work: (1) The shape of the dependence of the number of immunologically activated cells afterk-fold immunization on the immunizing dose and the rate of elimination of antigen was established. (2) In studies on the influence of the magnitude of a single antigen dose on the readiness for the secondary reaction (expressed as the number of immunologically activated cells present at the time of injection of the secondary antigen dose), we found that with increasing antigen dose the number of immunologically activated cells increases until it reaches its peak at the optimum antigen dose; then a decrease starts to occur. The range of doses of antigen causing approximately similar (and high) readiness for the secondary response is broader with antigens that are eliminated faster from the organism. (3) A method for the estimation of the optimum dose of antigen and of the number of persisting immunologically activated cells after this antigen dose is presented. This method can be used provided certain knowledge concerning the particular experimental system is available.

On contacts of immunocompetent cells with antigen (Note on a probability model)

This communication continues with the mathematical formulation and solution of some problems connected with the beginning of the immunological reaction. This paper generalizes some previous results concerning the probability of the event that such a contact of an immunocompetent cell (ICC) with antigen, which is followed by the differentiation of this cell towards the antibody forming cell (AbFC), takes place. Previous papers considered the onset of the differentiation of an ICC caused by the contact of this cell with at least a certain threshold amount of antigen (assuming that these contacts form a non-homogeneous Poisson process). This paper is based on the more general and more realistic assumption thatn such contacts are necessary for the stimulation of ICC differentiation (this new assumption has its origin in some new biological findings on the nature of the contact considered, and corresponds with the idea that the diffentiation of ICC does not begin until the antigen is bound on a certain fixed number of receptors on the cell surface). Under this assumption, the probability of the event that the differentiation of the cell begin at all (i.e. that at leastn contacts will take place), and the probability distribution of the epoch of the beginning of the differentiation (i.e. of the epoch at which thenth contact take place), are derived.— If necessary, these new forms of probability distributions may be used (instead of previous ones) as building stones in models of ICC differentiation.

Influence of the amount of antigen and the interval on the secondary reaction

The course of the revaccination reaction in mice immunized with different doses of sheep red blood cells was determined at different intervals after the primary stimulus. The maximum level of haemagglutinating antibodies in the secondary reaction was found after a high primary and secondary antigenic stimulus. On the contrary, if the level of haemolytic antibodies was determined, the higher was the primary antigenic stimulus, the lower was the secondary antibody response. Differences between haemagglutinins and haemolytic antibodies were also manifested in the earlier onset of the maximum haemolytic secondary reaction (five months after the first dose of antigen); the maximum haemagglutination response was not attained until eight months after the primary dose of antigen. The results comfirm that the basis of preparation for the secondary reaction is proliferation of immunologically activated Y cells; differences in the haemolytic and haemagglutination response are related to differences in the character of the antigenic determinants of sheep red cells.

On the estimation of the number of antibody-forming cells

The variability of the number of antibody-forming cells (AbFC) on using the plaque method is discussed. In the first part of the study it is shown on the basis of experimental data that the number of AbFC in a standard number of spleen cells has approximately Poisson distribution in one animal if the number of AbFC in a suspension is small, but that as the number of AbFC rises (even if the number of test cells in the given volume remains the same), variance increases more rapidly than the mean value and negative binomial distribution is a better probability model. The maintenance of conditions for Poisson distribution is evidently also related to the absolute number of test cells in a given volume, however. If the number of spleen cells in a given volume is raised, it is impossible to maintain complete homogeneity of the suspension; the cells form agglomerates, resulting in greater variability of the number of cells in individual drops. Under certain conditions, however, negative binomal distribution tends to Poisson distribution. In the second part, the question of determination of the error of estimation of the number of AbFC, expressed as percentages of the true value, is studied. Presuming Poisson distribution, it is pointed out that it is impossible to predetermine a fixed limit of the experiment, i.e one which will ensure for a given confidence level that the empirically determined value will not differ from the true value by more than a predetermined percentage of the true value; for routine use, however, a nomogram for the approximate estimation of the degree of error with which we work is suggested. Alternatively, the sequential method can be employed for estimating the number of AbFC with a given degree of error, but this statistical method is more exacting as regards both the preparation and the execution of the experiment.

Class IgG, IgM and IgA Antibodies against Staphylococcus aureus Antigens in Human Serum and Saliva

Using the ELISA method antibodies against the sonicate, teichoic acid (TA) and exoproducts ofStaphylococcus aureus were determined in sera and saliva of healthy individuals. Main serum antibodies against all the antigens used were shown to be class IgG antibodies. However, antigens of the sonicate stimulated significantly even the systemic IgA response. In the saliva class IgA antibodies predominated, but IgG antibody levels against TA and exoproducts approached the level of IgA antibodies. Levels of IgM antibodies against all antigens tested were low in both the serum and saliva which corresponds with the anamnestic type of response. On the basis of these results one may assume that not only IgG, but also IgA antibodies are important in the systemic immunity against staphylococcal infection and in the immunity of mucous membranes; besides IgA, even class IgG antibodies play an important role.

TheX → Y → Z scheme after 23 years

Mathematical modelling of the course of the immune response is undoubtedly one of the most progressive and most promising areas of modern immunology. Mathematical models (along with computer programs) can be taken as “the only means of thoroughly testing and examining a large and intricate theory” (Partridgeet al. 1984). The first phase of construction of mathematical models is the formulation of assumptions based on the knowledge of the facts to be modelled (manifested usually in a scheme of the presumed course of the modelled process). The first mathematical models of immune response were based on the hypothesis of a two-stage differentiation of cells participating in the humoral response, published in Prague 23 years ago (Sercarz and Coons 1962; Šterzl 1962) and illustrated by theX →Y →Z scheme. Many contemporary mathematical models still stem from this scheme which undoubtedly fits the fundamental data concerning the immune system.

Variances in the levels of serum lysozyme in x-irradiated mice.

The level of serum lysozyme in mice varies in relation to the dose of irradiation in several phases. High doses result in a progressive decrease whereas a decrease on the first and about the ninth day is observed after irradiation with lower doses. A rise in lysozyme level occurs on the third day. Enhancement of lysozyme levels was observed after application of 20—50 r. Administration of lysozyme did not affect the deaths of mice receiving with massive doses of irradiation.

Effect of x- radiation and 6-MP on the secondary antibody response.

The course of the secondary response in mice and rabbits immunized with sheep red cells and treated with X-rays or 6-mercaptopurine during the primary or secondary response was studied. X-irradiation or the administration of 6-MP during the primary reaction did not suppress preparation for a secondary reaction in mice, while in rabbits it did. The differences in these results are attributed to differences in metabolic activity, i.e. in the rate of recovery of the function of the lymphatic tissue, in the two species. The secondary reaction in mice was completely inhibited if they were irradiated when the proliferation phase following the primary stimulus had ended, e.g. six months after primary immunization.