Immunological characterization of a γδ T‐cell stimulatory ligand on autologous monocytes

Abstract

SUMMARYBovine cd T cells are stimulated to proliferate by autologous monocytes. This is referred to as the autologous mixed leucocyte reaction (AMLR). It has been shown previously that the stimulatory component is constitutively expressed on the monocyte plasma membrane and is a protein or has a protein moiety. Here we showed that cd T-cell responses to the monocytes requires interaction with the T-cell receptor because Fab 1 fragments of a monoclonal antibody (mAb) that reacts with the d chain of the T-cell receptor blocked proliferation in the AMLR. Monocyte molecules involved in stimulation were also characterized further by biochemical and immunological methods. A mAb, named M5, was generated by immunizing mice with bovine monocytes and shown to block the ability of monocytes to stimulate in the AMLR. Treatment of monocytes or monocyte membranes with high salt, chelating agents or phospholipase C did not affect their ability to stimulate cd T-cell proliferation or reactivity with mAb M5 indicating the ability of monocytes to stimulate does not involve peripheral membrane components or a glycosyl-phosphatidylinsositol (GPI)-anchored components. Hence it was concluded that the stimulation occurred as a result of intergral membrane proteins including that recognized by mAb M5. The ligand for mAb M5 was on all bovine monocytes and to a lower level on granulocytes but not on lymphocytes. MAb M5 also reacted with sheep monocytes but not with human monocytes or murine macrophages, in agreement with a previous reports that sheep monocytes but not human or mouse mononuclear phagocytes have the capacity to stimulate bovine cd T cells in in vitro cultures. The level of expression of the M5 ligand was not altered by c-irradiation or culture of monocytes with lipopolysaccharide but it was decreased following culture with interferon-c-containing cell culture supernatants.

Human adenosine deaminase 2 induces differentiation of monocytes into macrophages and stimulates proliferation of T helper cells and macrophages

“…The proliferation of CD4 ϩ T cells is antigenindependent. Our observations are similar to the phenomenon known as the autologous MLR, where it was shown that bovine monocytes stimulate the proliferation of autologous ␥␦ T cells [32]. The effect of ADA addition is most prominent at low concentrations of monocytes, where the amount of proliferating CD4 ϩ T cells can be several-folds higher than in the absence of the enzymes (Fig.…”

Mononuclear cell subsets in bronchoalveolar lavage fluid duringDictyocaulus viviparusinfection of calves: a potential role for γ/δ TCR‐expressing cells in airway immune responses?

“…Studies of bovine γ/δ TCR-expressing cells have to date, for example, shown that these cells recognize conserved antigens induced by or derived from Theileria parva in an MHC-unrestricted fashion (28), present antigen to CD4-expressing cells and produce an array of cytokines known to influence the activities of antigen-presenting cells as well as CD4-expressing cells (29). It has also been shown that bovine γ/δ TCR-expressing cells can be stimulated to proliferate by autologous monocytes (30).…”

Regulation of Numbers of Macrophages in the Endometrium of the Sheep by Systemic Effects of Pregnancy, Local Presence of the Conceptus, and Progesterone

“…Function of these macrophages during pregnancy is not known but evidence exists to indicate a role in immunoprotection of the conceptus, 11–14 apoptosis, 4,10 trophoblast growth, 15 and parturition 5,16 . In sheep, it is possible that endometrial macrophages participate in the increase in number and granularity of γ δ T cells seen in endometrial luminal epithelium 20,21 because autologous monocytes can stimulate proliferation of bovine γ δ T cells 22 …”