Specific priming of mouse thymus-dependent lymphocytes to allogeneic cells in vitro

A novel noninvasive method to detect rejection after heart transplantation

Prompt and accurate detection of rejection prior to pathological changes after organ transplantation is vital for monitoring rejections. Although biopsy remains the current gold standard for rejection diagnosis, it is an invasive method and cannot be repeated daily. Thus, noninvasive monitoring methods are needed. In this study, by introducing an IL-2 neutralizing monoclonal antibody (IL-2 N-mAb) and immunosuppressants into the culture with the presence of specific stimulators and activated lymphocytes, an activated lymphocyte-specific assay (ALSA) system was established to detect the specific activated lymphocytes. This assay demonstrated that the suppression in the ALSA test was closely related to the existence of specific activated lymphocytes. The ALSA test was applied to 47 heart graft recipients and the proliferation of activated lymphocytes from all rejection recipients proven by endomyocardial biopsies was found to be inhibited by spleen cells from the corresponding donors, suggesting that this suppression could reflect the existence of activated lymphocytes against donor antigens, and thus the rejection of a heart graft. The sensitivity of the ALSA test in these 47 heart graft recipients was 100%; however, the specificity was only 37.5%. It was also demonstrated that IL-2 N-mAb was indispensible, and the proper culture time courses and concentrations of stimulators were essential for the ALSA test. This preliminary study with 47 grafts revealed that the ALSA test was a promising noninvasive tool, which could be used in vitro to assist with the diagnosis of rejection post-heart transplantation.

Once a killer, always a killer: from cytotoxic T cell to memory cell

The control of the differentiation pathways followed by responding CD8(+) T cells to produce protective memory cells has been intensely studied. Recent developments have identified heterogeneity at the effector cytotoxic T-lymphocyte level within which a bona fide memory cell precursor has emerged. The challenge now is to identify the cellular and molecular factors that control this developmental pathway. This review considers aspects of the regulation of the induction of effectors, the transition of effectors to memory cells, and the dynamics of the memory population.

In vivo responses of alloreactive lymphocytes stimulated in vitro. Skin graft rejection mediated by MLR-Primed lymphocytes

Mouse lymphocytes that have been primed in vitro against alloantigens show a specific increase in cells reactive to the priming antigens in mixed lymphocyte response (MLR) and include cells that are specifically cytotoxic in vitro. The primed population also contains cells capable of causing rejection of skin grafts when injected into nude mice. Functional enrichment of cells capable of rejecting skin grafts bearing specific alloantigens and depletion of cells capable of rejecting a third-party graft have been shown. Priming the cells a second time in vitro may result in a moderate enrichment of cells capable of rejecting the specific graft and depletion of cells reactive to third-party skin compared with once-primed cells. These findings support the prediction that the MLR is an in vitro model of allograft responses in vivo.

Phosphotyrosine phosphatases are involved in reversion of T lymphoblastic proliferation

Resting T lymphocytes can be activated by mitogens or antigens to become T blasts, which revert spontaneously both in vivo and in vitro in extended cultures to secondary, memory T lymphocytes. We have studied the role of phosphotyrosine phosphatases (PTPase) in the reversion of lymphoblasts in extended, phyto-hemagglutinin-stimulated cultures of human T lymphocytes. Membrane-associated PTPase activity is high in resting T cells, but decreased during mitogen-induced blast transformation. When the blasts were reverting to lymphocytes, the PTPase activity increased more than twofold concomitantly with an elevated surface expression of CD45. When T blasts from phytohemagglutinin-activated cultures were kept in the presence of sodium orthovanadate, an inhibitor of PTPase, they maintained their lymphoblastic proliferation and did not revert to resting lymphocytes. This was accompanied by retention of a 48-kDa phosphotyrosine-containing protein. Our data indicate an important role for PTPase in the transition of lymphocytes from an activated to a resting stage.

Analysis of HLA-D micropolymorphism by a simple procedure: RNA oligonucleotide hybridization

Recent progress in the molecular genetics of HLA class II antigens has revealed the existence of multiple loci and of a large degree of polymorphism, with more individual alleles than was expected. An accurate detection and analysis of this extensive polymorphism is essential for optimal HLA typing for transplantation and for a reevaluation of HLA-disease association. Because of the limitations of the current typing methods, including restriction fragment length polymorphisms, we have proposed a DNA typing procedure based on hybridization with loci- and allele-specific oligonucleotides. Here we present a much simpler way of analyzing class II micropolymorphism down to the level of single nucleotide differences. RNA oligonucleotide typing (ROT) relies on RNA dot blots and requires 10-20 ml of blood. It is shown that with appropriate oligonucleotide probes, ROT can reliably and unambiguously identify any polymorphism at any of the HLA loci, including new alleles, not identified with previous methods. This illustrates the importance of oligonucleotide typing to optimize HLA matching, in particular for transplantation involving unrelated donors.

Further studies on psoriasis-associated HLA-Dw/DR7 using PLT cells primed against a familial psoriasis-linked HLA haplotype

The products of the HLA-D region and their correlation to psoriasis vulgaris was studied using the primed lymphocyte typing (PLT) assay. In families with one healthy and one psoriatic parent and one psoriatic child primary MLC (mixed lymphocyte culture) stimulation was carried out between responder cells from the healthy parent and stimulator cells from the psoriatic child. In this way 21 PLT reagents directed against putative psoriasis-associated lymphocyte activating determinants were produced. Three reagents that gave clear bimodal stimulation patterns against lymphocytes of 51 psoriasis patients were further tested against 78 controls. Specificity of these reagents was studied using homozygous typing cells (HTC's) as stimulators. Compiled data show that cells from DR7 positive psoriatic patients give higher restimulation of these PLT reagents than do cells from healthy DR7 positive controls. In addition, a higher frequency of psoriasis patients compared to controls gave significant restimulation. Therefore we concluded that these PLT reagents recognized at least partly different DR7 associated determinants in the psoriasis patients and in controls. The reason is either that psoriasis patients carry a different lymphocyte activating DR associated specificity or, alternatively, that restimulation was caused by products of a distinct psoriasis associated locus in linkage disequilibrium with D/DR7 or of a determinant recognized together with D/DR7 as a restriction element. These data further support the notion that psoriasis is a disease with primary HLA associations to both class I and class II MHC genes.

The glycosphingolipid globoside as a serological marker on cytolytic T lymphocyte precursors and alloantigen-responsive proliferating T lymphocytes in murine spleen

Biochemical analyses of murine lymphocytes have shown that the glycosphingolipid globoside (Glo) is present exclusively on alloantigen-stimulated murine T lymphocytes (Gruner, K. R., Van Eijk, R. V. W. and Mühlradt, P. F., Biochemistry 1981. 20: 4518). An anti-Glo antibody has now been raised in rabbits immunized with purified antigen. Most activity was recovered in the IgM fraction. The specificity of the antibody was ascertained in an enzyme-linked immunosorbent assay with purified glycosphingolipids bound to the solid phase. In antibody-dependent complement lysis experiments the anti-Glo eliminated about 20% of nylon wool-nonadherent splenic T cells of CBA/J mice. To determine the functional identity of these Glo+ cells, the effects of Glo+ cell elimination on mitogen stimulation with concanavalin A and lipopolysaccharide, as well as the effects on the mixed lymphocyte culture (MLC) reaction and cell-mediated lympholysis with mitomycin-treated DBA/2 splenocytes as stimulator cells were studied. Whereas lipopolysaccharide stimulation was not affected by elimination of Glo+ cells, there was a slight inhibitory effect on the concanavalin A stimulation, and a severe inhibition of the MLC reaction and the generation of H-2d-specific cytolytic T lymphocytes. Addition of interleukin 2 increased the MLC reaction, but interleukin 2-saturated cultures were also severely inhibited by anti-Glo and complement treatment. Combined treatment with anti-Glo and anti-Lyt-1 or anti-Lyt-2 antibodies, and determination of cytolytic T lymphocyte precursor frequencies in limiting dilution cultures after Glo+ cell elimination showed that a large proportion of T cells proliferating in a primary MLC are Lyt-1+,2+,3+Glo+, whereas in secondary MLC they are Lyt-1+,2-,3-,Glo+. Fifty % of the cytolytic T lymphocyte precursors in primary as well as secondary MLC are Glo+. The Glo marker is lost upon differentiation to cytolytic T lymphocyte effector cells. It is discussed herein that Glo is a marker for alloantigen-stimulated precursor T lymphocytes of both helper and cytolytic T cells.

Stimulation in primary MLR caused by a PLT defined non-HLA-D/DR determinant, EP1

The influence in primary mixed lymphocyte culture reaction (MLR) of a primed lymphocyte typing (PLT) defined non-HLA-D/DR determinant, EP1, was investigated. In primary MLR between HLA-D/DR compatible lymphocytes, the response of the lymphocytes from 14 EP1-negative HLA-D/DR heterozygous individuals towards two EP1-positive homozygous typing cells (HTCs) was on an average approximately 35% higher than the response towards two EP1-negative HTCs (P less than 0.01). The strength of the MLR between lymphocytes from 25 EP1-negative and 10 EP1-positive individuals matched for two HLA-D/DR antigens was investigated. The average responses of EP1-negative lymphocytes against EP1-positive lymphocytes were approximately 40% higher than the average responses against EP1-negative lymphocytes (P less than 0.01). These data indicate that the PLT defined determinant EP1 causes stimulation in primary MLR.

Typing for human alloantigens with the primed lymphocyte typing (PLT) technique with notes on the interpretation of PLT data

A typing system for HLA-D/DR-associated PLT-defined determinants, which have been called "DP" antigens, is reported. Some of the results concerning a data interpretation system, the reproducibility of PLT results, and the correlations between the results of HLA-D, -DR, and DP typing are presented. Also, a "new" human alloantigen, EP1, not belonging to the series of DP antigens, is defined with PLT.

Technical aspects of the primed lymphocyte typing (PLT) technique

The influence of different culture conditions in the primary and secondary cultures of the primed lymphocyte typing (PLT) technique was investigated with special reference to the discriminatory capacity of the PLT-cells generated. In the primary cultures, the maximal yield of PLT-cells was observed early (about day 7) and decreased thereafter, while the maximal specificity was obtained considerably later (about day 14). In the secondary cultures, the optimal culture time was in the interval 42 h - 72 h, and up to this culture length, gamma-irradiation (2,200-8,800 rad) of the secondary stimulators had no effect on the 14C-thymidine uptake of the cultures. In U-form microtiterplates, the number of PLT-cells per well should not be less than 2.5 X 10(4), and higher PLT-cell numbers (e.g. 5.0 X 10(4) per well) may confer further robustness upon the technique. The PLT-cell response and the discrimination was only slightly influenced by the number of secondary stimulator cells in the interval 5 X 10(4) to 2 X 10(5) cells per well. Freezing of the PLT-cells under controlled conditions resulted in a minor loss of viable eosin-excluding cells, while the specificity of the PLT-cells was unaffected. Even when the culture conditions are standardized, it is necessary to perform a normalization of the data in order to obtain reproducible results. The normalization procedure should include a compensation for the variation in (i) the general responding capacity of each PLT-cell and in (ii) the general stimulatory capacity of each secondary stimulator.

A "new" primed lymphocyte typing (PLT) defined DP-antigen associated with a private HLA--DR antigen

We have recently described a "new" private HLA-DR antigen, DR"LTM", which has a frequency of approximately 0.6% in Danes. Primed Lymphocyte Typing (PLT) cells directed towards DR"LTM"-associated determinants were generated in vitro by haplotype primings in two unrelated families with DR"LTM" positive individuals. Both PLT-cells reacted in parallel and gave positive reactions with (i) two unrelated and (ii) eight related individuals, all of whom were DR"LTM"-positive. Both PLT-cells gave negative reactions with (i) 38 unrelated and (ii) 15 related DR"LTM"-negative individuals. Thus, there was total agreement between the results obtained by HLA-DR typing with the antiserum "LTM" and by PLT-typing with these two haplotype primed PLT-cells. None of the DP"LTM"-positive individuals carried more than one of the antigens HLA-Dw/-DRw/DP1-8 and the local specificity D/DP"H". Accordingly, this "new" PLT-defined antigen, DP"LTM", most probably belongs to the series of HLA-D/DR-associated DP-antigens previously described.

Typing for HLA-D/DR associated DP-antigens with the primed lymphocyte typing (PLT) technique

A total of 74 healthy unrelated random individuals and 36 patients with juvenile rheumatoid arthritis (JRA) were typed for HLA-D antigens with the homozygous typing cell technique and typed for HLA-D/DR associated DP-antigens with the primed lymphocyte typing (PLT) technique. All patients and some of the controls were also HLA-DR typed with a limited battery of anti-DR sera. Selected PLT-cells, specific for the HLA-D/DR antigens D/DRw1-8 and the local specificity D"H" were used. The results of the PLT-experiments were evaluated with the Normalized Median Response (NMR) method and the further procedure of DP-antigen assignment was analyzed. The DP-antigen assignments could be done solely according the NMR-values in approximately two thirds of the individuals. In the remaining individuals, further interpretation of the experimental data had to be done for the assignment of DP-antigens. The correlation coefficients were estimated between the HLA-D assignments and (i) the individual PLT-cell NMR-values with a fixed cut-off for positive reactions and (ii) the DP-antigen assignments. These coefficients were 0.79 and 0.92, respectively. The correlations between HLA-D, -DR and DP-antigen assignments of the specificities HLA-D, -DR and DP1, 2, 3, 4, 7 and 8 were analyzed in 42 controls and 36 JRA patients. The total correlation coefficients were: (i) HLA-D/DR: r = 0.78; HLA-DR/DP: 0.77; and HLA-D/DP: 0.96. The DP-antigen assignments correlated significantly better with HLA-D than with the HLA-DR antigen assignments, which does not agree with other studies. The DP-antigen frequencies among the controls were calculated and the estimated sum of gene frequency corresponding to definable DP-antigens was 0.94 indicating that about 12% of random individuals possess as yet undefined DP-antigens.

Generation of HLA-D specific primed lymphocyte typing (PLT) cells and cross-reactions of PLT-cells primed with homozygous typing cells

An approach for the selection of HLA-D specific primed lymphocyte typing (PLT) cells is described. The responder cells were primed with homozygous typing cells. Reproducible extra reactions were found and were analyzed in relation to HLA-D antigens defined by homozygous in cells (HTC's). The secondary response of 105 different PLT-cell combinations generated by 29 different primary responders against 19 different homozygous typing cells of the specificifies Dw1 to Dw8 and the local specificity "H" were tested in secondary PLT toward 17 different homozygous typing cells and 10 heterozygous cells. Cross-reactions were defined as reactions equal to or higher than the lowest HLA-D specific reaction observed. The entire experimental design and data analysis gave rise to a conservative definition of cross-reactivity. Two main groups of cross-reacting HLA-D determinants seem to exist: (i) Dwl, 3, 4, 7, and the local specificity "H", and (ii) Dw2, 5, 6, 8, and "H". The primary pairwise cross reactions were in group (i): Dw1-3, Dw1-"H", Dw3-4, Dw3-7, Dw7-"H", and in group (ii): Dw2-6, Dw2-8, Dw5-8, and Dw5-"H". The existence of such cross-reactions is likely to interfere with the results of PLT-typing and should be taken into account when attempts are made to develop HLA-D specific PLT-cells.

Data reduction in HLA-D typing with the primed lymphocyte typing (PLT) technique. the normalized median response (NMR)

We describe here a simple non-parametric method for the evaluation of data obtained from primed lymphocyte typing (PLT) experiments. The method is designed to compensate for both differences in the PLT responsiveness and stimulatory capacity by a double normalization procedure based on a representative negative reaction (the median) for each PLT-cell and for each secondary stimulator. The index of response is called the Normalized Median Response (NMR). The NMR-method was developed from data from one of a series of PLT experiments aimed at HLA-D typing. The NMR-method was applied to eight other PLT experiments and was compared to two other calculation methods based on the maximal response of each PLT-cell: (i) a method without compensation for stimulator variation, and (ii) a method including non-parametric compensation for stimulator variation. The eight experiments involved 37 different PLT cells tested against 74 different stimulating cells yielding a total of 1,334 secondary combinations. The NMR-method descriminated significantly better than the other methods when the results were compared to the HLA-D types obtained with homozygous typing cell technique. In particular, the number of extra positive reactions was diminished by the NMR-method. The reproducibility and the sources of variation were studied in the eight experiments and in five additional experiments. The NMR-method reduced the combined priming-to-priming variation and day-to-day variation to a level comparable to the variation between duplicate testings of the same PLT cell tested towards the same set of secondary stimulators in the same secondary PLT experiment.

Secondary responses of alloantigen-primed dog lymphocytes

The usefulness of Primed Lymphocyte Typing (PLT) for recognizing Lymphocyte Defined (LD) determinants of the Major Histocompatibility Complex of the dog (DLA) was assessed in 10 separate experiments. Application of a technique described for human cell to peripheral blood lymphocytes of dogs gave reproducible, informative results. DLA LD determinants were shown to be of major importance in secondary responses of alloantigen "primed" lymphocytes, but other, a yet undefined, factors also appeared to play a role in the assay.

Generation of virus-specific cytotoxic T cells in vitro. I. Induction conditions of primary and secondary Sendai virus-specific cytotoxic T cells

H-2-restricted cytotoxic T cells specific for Sendai virus were generated in vitro in a primary response from normal mouse lymphocytes cultured in the presence of infective as well as inactivated Sendai virus. Antigen-presenting cells of different origin, including T cells, were found to be effective stimulators. Antibodies to Sendai virus were shown to inhibit the activation of specific precursor killer cells when added to cultures before, but not after, the addition of viral antigen. Data obtained by Lyt phenotyping, revealed that precursor killer cells specific for Sendai virus reside in the Lyt-2,3+ T cell population and that Lyt-1,2,3+ T cells are not required for the generation of cytotoxic lymphocytes. Different activation kinetics were demonstrated for primary and secondary antiviral cytotoxic responses, and the analysis of the proliferation and stimulation requirements suggests qualitative differences.

Studies on T lymphocyte activation. I. Requirements for the mitogen-dependent production of T cell growth factors

Conditioned media (CM) obtained from concanavalin A (Con A)-stimulated spleen cell cultures maintain mitogen-derived T cell blasts in exponential growth for indefinite periods of time. Such purified T cell blasts do not respond to Con A, and the growth-promoting activity in CM is independent of the mitogenic lectin used for its production. However, the appearance of activity in CM is Con A dose-dependent. Furthermore, the production of these T cell growth factors is independent of B cells, while it requires both T cells and nontheta-bearing, probably Ia-positive cells present in normal and nude spleens. On the other hand, the T cell blasts which are reactive to the growth factors, neither produce CM by themselves nor can they cooperate with nude spleen cells for its production, in the presence of a mitogenic lectin. Since the concentration of growth factors in CM determines the extent of T cell growth, we propose that the growth of some T cells is necessarily dependent upon the activity in CM described here and, consequently, that the basis for T cell activation is the induction of such growth factors.

Specificity of human lymphocytes primed against allogeneic cells in vitro. II. Discrimination and cross-reactivity in repeated priming

When studying the specificity of human lymphocytes primed in vitro against HLA-D determinants on allogeneic cells, it was found that specific restimulation of the primed cells 10 days after the first priming did not influence their discriminatory power compared to cells primed only once. Likewise, priming to one HLA-D determinant and repeated priming against another HLA-D determinant did not change the discrimination for the first priming antigen. Neither was there any increased relative reactivity to the second priming determinant. On simultaneous priming against two HLA-D determinants carried by two different stimulating cells, a good discrimination for both antigens was obtained compared to third party cells, but if the stimulations were separated by 24 h or more, the second priming was mainly without effect. Antigeneic competition is thought to be the mechanism involved in this early restriction of specificity.

Restimulation of PPD-stimulated lymphocytes: decreased responsiveness of prestimulated cells to a second challenge with PPD and PHA

Lymphocytes stimulated with purified protein derivative (PPD) were inhibited in their response to a second stimulation with PPD or phytohaemagglutinin (PHA). The degree of inhibition was related to the PPD concentration during prestimulation, the dose-response curve for inhibition resembling very much that of stimulation. The decreased reactivity was neither due to a toxic effect of PPD nor to altered proliferation kinetics of the prestimulated cells. Lymphocytes preincubated for 6 h or 16 days with PPD were equally refractory, and the non-reactivity persisted even if the cells were incubated without stimulant for 1 week or more. The prestimulated cells were able to suppress the PHA stimulation of fresh lymphocytes. These results indicate that the decreased reactivity of the prestimulated lymphocytes is due to the action of suppressor lymphocytes, generated during the primary stimulation.

Anomalous mixed lymphocyte culture reactivity between HLA--A, --B, --C, --DR identical siblings

Complete HLA typing including HLA--A, --B, --C, --DR (D related B cell typing), --D, mixed lymphocyte culture (MLC), and primed lymphocyte testing (PLT), together with complete red blood cell (RBC), glyoxalase (GLO), GBG (Factor B), and phosphoglucomutase 3 (PGM3) typings were performed on a informative family. The five siblings inherited the four possible combinations of parental HLA haplotypes, and two of the siblings were HLA--A, --B, --C and --DR identical. Repeated MLC testing of the family revealed positive mixed lymphocyte reactivity in all combinations. B cell typing for the DR specificities demonstrated no variation from the expected inheritance pattern and specifically no recombination event. GBG and GLO typings militated against a recombination involving the paternal chromosome. HLA--D testing revealed that only one of the HLA--A, --B, --C, and --DR identical siblings gave typing responses to the HLA--Dw3 specificity present on that maternal haplotype. Utilizing HLA haploidentical combinations, lymphocytes were primed against the four parental haplotypes and the non-Dw3 haplotype of interest (Aw24--B8--DRw3--LDY) in the PLT. The sibling inheriting this haplo-type did not restimulate cells primed against the A2--B40--DRW6--LDY specificity. Furthermore, no discrimination was observed in the restimulation of lymphocytes primed against this haplo-type. Possible interpretations of these family data include: a spontaneous mutation, non-major histocompatibility locus (MHC) stimulation, and HLA--DR/D recombination.

Clonal priming of human lymphocytes with soluble microbial antigens: high-dose paralysis, restoration, and autologous leukocyte preference

Lymphocytes stimulated in appropriate leukocyte cultures undergo blastogenesis and proliferation for a finite period of time. With specific antigens the proliferative response peaks usually between 4 and 8 days, after which the blastoid cells revert to small lymphocytes. Lymphocytes "primed" in this manner can be restimulated to proliferate only by the same antigen with which they were incubated and only with an adequate amount of a self-specific, autologous, somatic product(s). First or "primary" leukocyte cultures stimulated by optimal or supraoptimal concentrations of soluble protein antigens (purified protein derivative (PPD), tetanus toxoid, Candida albicans) will undergo proliferation in the first culture, but the increased number of small lymphocytes that can be visualized after 10--14 days often fail to respond to any stimulus in second (secondary) or "primed" cultures. However, when fresh X-irradiated autologous cells are re-added in appropriate amounts, vigorous accelerated proliferation takes place. Addition of allogeneic cells to antigen-primed populations has one of three effects: (1) no effect (complete restriction); (2) in some instances allogeneic cells restore a significant response to the specific antigen but almost never to the same degree as autologous cells; and (3) allogeneic cells can also induce high levels of accelerated responsiveness without added antigen. These findings are discussed in the context of a working hypothesis that self-specific factors are involved in all specific immune responses. The combination of antigen and self-specific factors may lead to a quantitatively unique immune response to all antigens in each individual. The preferential response to antigen in conjunction with autologous rather than allogeneic leukocytes suggests that self-specific products are required for recognition of soluble microbial antigens.

At least two loci of the major histocompatibility complex can determine mixed lymphocyte stimulation in the rat

Analysis of a recombinant haplotype of the major histocompatibility complex showed that two genetically separable loci (or groups of loci), LD--1 and LD--2, determine mixed lymphocyte stimulation in the rat. LD--1 maps into the H--1B region which contains the Ir genes and is associated with strong, mixed lymphocyte stimulation. LD--2 maps into the H--1A region and determines weak stimulation. LD--1 and LD--2 determinants can be detected by primed lymphocyte typing.

Detection of HLA-D clusters and segregation studies using primed LD typing

By testing a group of PLT cells over a panel of unrelated restimulating cells, the PLT's could be grouped into clusters according to their ability to discriminate antigen(s) in unrelated cells. The PLT clusters broadly correlated with the homozygous typing cell-defined HLA-D clusters represented on the panel. The PLTs grouped together clearly segregate with a particular HLA haplotype when tested in both unrelated families not possessing the sensitizing haplotype and in the family with the sensitizing haplotype. No influence of HLA SD antigens could be observed in PLT restimulation in the segregation studies.

T cells which proliferate in response to concanavalin A include cells which proliferate in mixed leucocyte reactions

Selection in long-term culture of alloreactive T cells, by successive in vitro restimulation with semi-allogeneic cells, results in primed responder cell populations which maintain full proliferative reactivity to allogeneic cells as well as to the T cell mitogens concanavalin A (Con A) and phytohemagglutinin (PHA) but are depleted of cells which can effect target cell destruction in either a specific or nonspecific manner. Con A-induced T cell blasts (selected by velocity sedimentation) can revert to small resting lymphocytes in the presence of inert "filler" cells. Con A blasts which have reverted, readily proliferate in response to Con A or allogeneic stimulator cells but are largely depleted of effector killer cells and PHA-responsive cells.

Activation of human suppressor cells in mixed lymphocyte cultures

Lymphocytes transferred from 6-day-old human mixed lymphocyte cultures (MLC) inhibited the response to allogeneic cells of freshly taken lymphocytes autologous to the transferred MLC-responding cells. No specificity for this cell-dependent suppression could be determined. The inhibitory effects of the suppressing cells could be abrogated by moderate X-ray irradiation and significantly reduced by pretreating them with an anti-Ia-like antiserum and complement. The human suppressor cell responsible for the observed effects therefore appears to carry determinants equivalent to the murine Ia alloantigens.

Clonal priming of human lymphocytes: Specificity and cross-reactivity of cellular immune reactions

Clonal priming in response to chemical and microbial antigens which defines the specificity of cellular immune reactions, was demonstrated by culture techniques. Human leucocyte cultures stimulated with specific antigens typically show peak levels of D.N.A. synthesis after 5 to 7 days in culture. Such primary leucocyte cultures were incubated for 10-20 days, then the cells were gently centrifuged and resuspended in fresh RPMI 1640 with 20% plasma. These secondary or primed cultures typically showed less than 1000 c.p.m. after 48 hours. However, if the original antigenic stimulant was added, specific accelerated responses were seen by 48 hours in the secondary cultures. Lymphocyte clones in these sceondary cultures primed with dinitrophenylated (D.N.P.) antigens (from subjects sensitised to dinitrochlorobenzene) showed enhanced D.N.A. sythesis in response to the same dinitrophenylated antigens and showed varible accelerated responses to related chemically modified antigens. However, D.N.P.-activated clones in these secondary cultures did not show enhanced responses to microbial antigens even though the lymphocytes had been highly responsive to tetanus toxoid and other microbial antigens in primary cultures. The specificity of this clonal activation was further demonstrated by the enhanced response of secondary cultures of tetanus-toxoid-activated clones to tetanus toxoid but not to dinitrophenylated antigens. The abiltty to detect specificity and cross-reactivity of cellular immune reaction has broad implications for investigations of cellular immunity as well as many potential applications in the diagnosis and understanding the patogenesis of inflammatory and neoplastic diseases in which cellular immune discrimination may be involved.

Lymphoblastoid cell lines of homozygous typing cells used for sensitization in PLT

Lymphoblastoid cell lines of homozygous typing cells were used as the sensitizing cells in MLC to prepare PLT cells. Results obtained using such cells against a panel of restimulating cells were compared to those obtained using regular PLT cells in which priming had been accomplished with normal peripheral blood lymphocytes. It appears that lymphoblastoid cell lines can be used for this purpose; the advantages of such an approach are given.

Generation of T memory cells in one-way mixed lymphocyte culture. IV. Primary and secondary responses to soluble and insoluble membrane preparations and to ultraviolet-light-inactivated stimulator cells

Neither normal CBA (H-2k) nor purified spleen T cells respond in vitro to soluble or insoluble membrane preparations or to ultraviolet-light-inactivated stimulator cells of the allogeneic DBA/2 (H-2d) strain. However, CBA spleen cells deprived of phagocytic cells show a slight proliferative response under these conditions. After being primed against mitomycin-blocked DBA/2 cells in one-way mixed lymphocyte culture, the secondary blast-derived T 'memory' cells display a good secondary blast (proliferative) response to both membrane antigens and to ultraviolet-light-inactivated stimulator cells. In addition to this, the secondary T lymphocytes--in contrast to nonprimed T cells--respond by cytotoxicity when ultraviolet-light-inactivated cells are used as the second stimulant.

Lymphocyte activation. VIII. The application of a whole blood test to the quantitative analysis of PHA responsive T cells

In diluted blood predominantly T cells responded to purified PHA (pure leucoagglutinin Wellcome). Red cells and non-T mononuclear cells increased PHA responsiveness of T cells at concentrations present in the peripheral blood. Addition of polymorphonuclear leucocytes was a very slight further advantage. The incorporation of [3H] thymidine reflected the numbers of T cells in culture, although not perfectly linearly, since counts increased when more T cells were added to the cultures. It was therefore concluded that in cultures of diluted whole blood non-specific amplification mechanisms were provided and responses reflected the performance of stimulated T lymphocytes. Since the method is simple and the number of technical variables is relatively small, it is possible to establish a "normal" range of PHA responsiveness expressed in absolute counts per minute, and thus directly compare results from different laboratories.

Secondary cytotoxic allograft responses in vitro. II. Differentiation of memory T cells into cytotoxic T lymphocytes in the absence of cell proliferation

Murine cytotoxic T lymphocytes (CTL) were induced in "one-way" mixed lymphocyte cultures and their physical characteristics investigated by velocity sedimentation at 1 X g. The in vitro differentiation of progenitors of CTL into primary and secondary CTL was paralleled by characteristic changes in the size of the responder cells. Fractionated cells enriched for primary blast CTL reverted into clonally restricted "nonlytic" secondary T lymphocytes. Upon antigenic reexposure, these lymphocytes differentiated into secondary CTL within 18-32 h. This took place in the absence of cell proliferation and could be triggered by UV light irradiated allogeneic stimulator cells. It is suggested the different characteristics for the induction of either a primary or secondary cytotoxic T cell response reflect qualitative differences between unprimed T cells and memory T lymphocytes.