Detection of acceptor sites on human lymphocytes for antigen-specific T cell factors

Mouse antigen-specific T cell factors are absorbed by human peripheral blood lymphocytes at acceptor sites. The acceptors are products of HLA-linked genes, which may be human immune response genes.

Induction of an antibody response in cultures of human peripheral blood lymphocytes

A culture system is descirbed which provides adequate conditions for in vitro immunization of humand peripheral blood lymphocytes to heterologous erythrocytes. Making use of this method we could obtain, with a number of different donors, an antibody response which peaked at about day 8 of culture with 30-300 plaque-forming cells (PFC) per 10(6) input lymphocytes. However, in a number of experiments poor or negative results were obtained, even with donors that had previously given good response. This variability in the results was shown not to be due to a too low number of precursor cells present in the blood and could be overcome by treating the cells, before initiation of the culture, with a factor produced by mouse T cells educated to sheep erythrocytes (SRBC). Under these conditions a PFC responce was obtained which peaked at about day 8 and which in some experiments could be as high as 20,000 PFC per 10(6) input lymphocytes. Paralleling the increase in PFC was an increase in cell number. The cells recovered from the treated cultures were at all times more numerous than in the nontreated cultures. The height of both the proliferative and antibody-producing responses varied from experiment to experiment, a higher proliferative response, accompanying a higher PFC response. Although the mechanisms that are at the basis of the antibody response in vitro described in this paper still need to be clarified, this system may become a useful tool in studying the immune response in man.

Antigen-specific T-cell factor in cell cooperation and genetic control of the immune response

Cell interactions between thymus-derived (T) and bone marrow-derived (B) lymphocytes in the antibody response appear to involve soluble T-cell mediators known as 'factors.' This paper describes the properties of a T-cell factor that has specificity for the inducing antigen, a synthetic polypeptide (T, G)-A--L, and is able to replace T cells in the thymus-dependent antibody response to (T, G)-A--L. Besides antigen specificity, the main features of the molecule are that it is nonimmunoglobulin; it has a molecular weight of about 50,000; and it is a product of the I-A subregion of the H-2 complex (the mouse major histocompatibility complex). These properties suggest that the factor is closely related to the T-cell receptor, which may, by inference, also be a product of the H-2 complex. The factor cooperates well with allogeneic B cells. It can also be absorbed by bone marrow cells and B cells. Studies on the genetic control of the immune response to (T, G)-A--L using the T-cell factor indicate that two immune response genes in the H-2 complex are involved in genetic control, one expressed in T cells and the other in B cells. This two gene hypothesis has been confirmed by showing that an F1 between two low responders to (T, G)-A--L can be a high responder.

Antigen-specific T-cell factor in cell cooperation. Mapping within the I region of the H-2 complex and ability to cooperate across allogeneic barriers

Further mapping of the mouse T-cell factor specific for poly(Try,Glu)-polyD-LAla--polyLys is reported. It is shown to be a product of the I-A subregion of the H-2 complex by the use of antisera either raised specifically against or made specific, by absorption, for different regions of the H-2 complex. The factor cooperates across allogeneic barriers, e.g., when factor produced by one strian is combined with bone marrow cells of other H-2 incompatible strains.

Antigen-specific T-cell factors in the genetic control of the immune response to poly(Tyr,Glu)-polyDLAla--polyLys. Evidence for T- and B-cell defects in SJL mice

The cellular basis of the genetic control of the immune response to poly(LTyr, LGlu)-polyDLAla--polyLLys [(T,G)-A--L] in SJL (H-2s, low responder) mice has been investigated using T-cell factors. Thymocytes of SJL origin were educated to (T,G)-A--L and tested for their ability to produce an antigen-specific factor capable of cooperating in vivo with bone marrow cells of either SJL or C3H.SW (high responder) origin. SJL T cells were found to be incapable of producing such a cooperative factor, in contrast with results previously obtained with C3H/HeJ (low responders) and C3H.SW strains. Moreover, SJL bone marrow cells did not produce an antibody response to (T,G)-A--L, even when combined with factor produced by high responder (C3H.SW) mice. Thus, both T and B cells appear to be defective in the SJL strain in the response to (T,G)-A--L.

Antigen-specific T-cell factor in cell cooperation: physical properties and mapping in the left-hand (K) half of H-2

Mouse thymus cells, educated to poly(tyrosyl,glutamyl)-polyDLalanyl--polylysyl [(T,G)-A--L], release an antigen-specific factor on brief culture in vitro. The factor cooperates with bone marrow cells in the antibody response to (T,G)-A--L in irradiated recipients. Its mol wt determined from Sephadex G100 chromatography is in the region of 50,000. The factor is removed by specific antigen-coated columns, but not by anti-immunoglobulin (anti-Fab, anti-micro, anti-Fv) adsorbents. The factor is removed by alloantisera directed against the H-2 haplotype of the strain in which it is produced. Moreover, only antisera with specificity for the K side of H-2 were successful in removing the factor activity.

Tolerance to thymus-independent antigens. Characteristics of induction of tolerance to thymus-independent synthetic polypeptides

The conditions have been studied for induction of tolerance in mice to two thymus-independent multichain synthetic polypeptides, poly(DTyr,DGlu)-polyDPro--polyDLys, and poly(DTyr,DGlu)-polyLPro--polyLLys. The antigens are of very similar structure, differing only in the optical configuration of proline and lysine residues.

The tolerance thresholds were established by giving a single injection of antigen in solution in saline, followed later by challenge of antigen in adjuvant. For both antigens it was possible to induce high dose tolerance, which was preceded by a zone of priming at lower doses. In neither case was low zone tolerance observed. The induction of high zone tolerance was accompanied by a passing phase of antibody production in the case of poly(DTyr,DGlu)-polyDPro--polyDLys, but not in the case of poly(DTyr,DGlu)-polyLPro--polyLLys. Furthermore, the threshold doses for high zone tolerance for the two antigens differed by two orders of magnitude, being at about 100 μg per mouse for the former and at 1 μg per mouse for the latter. It appears that thymus-independent antigens, even if very similar structurally, can differ very markedly in the characteristics of their interaction with B cells.

Studies on antigenic competition. II. Abolition of antigenic competition by antibody against or tolerance to the dominant antigen: a model for antigenic competition

Antigenic competition between the Fc and Fab fragments of rabbit IgG in mice could be abolished by passive immunization with antiserum against the dominant antigen (Fc). The induction of tolerance to Fc also eliminated antigenic competition. Anti-Fd production, generally very poor in response to rabbit IgG, was considerably enhanced by these procedures, indicating that it is also subject to antigenic competition with Fc.

A model is proposed to explain antigenic competition which proposes that it is the `co-operative antibody' produced to the dominant antigen which acts as an inhibitor to antibody production to the suppressed antigen by competing for sites —presumably on macrophage membranes—where co-operation occurs.

The merits and difficulties of such an explanation are discussed.