Restricted recognition of H-2 subregion coded alloantigens in delayed-type hypersensitivity

Studies on the immunogenicity of an endogenously processed protein antigen in mice

We have examined the general immunogenicity of a non-replicating antigen which was introduced artificially into the endogenous pathway of antigen processing. EG7.OVA cells transfected with the OVA gene are efficient presenters of endogenously processed OVA and induced high levels of class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) in vivo. In addition, mice immunised with EG7.OVA cells developed immune responses more characteristic of class II MHC-restricted T cells, including IgG antibody production, systemic delayed type hypersensitivity (DTH) and a proliferative response to OVA in vitro. However, most of these responses were small, and EG7.OVA cells did not prime mice for secondary antibody or DTH responses. Thus endogenously synthesised, non-replicating antigens are poor stimulators of T cells which exploit the exogenous processing pathway. If vaccine vectors containing purified epitopes are to stimulate all T cells effectively, they will need to utilise strategies which enable direct entry to both antigen processing pathways.

The alloantibody response in the allogeneically pregnant rat. V. Absence of cell-mediated immunity in high responders

Allogeneically pregnant rats have been examined postpartum to determine whether they are sensitized against paternal class I antigens for cell-mediated immunity. This study was undertaken as this point is ambiguous. Since the response of the female to paternal MHC antigens is genetically controlled it is possible that the inability of some investigations to detect cell-mediated immunity against the paternal strain was due to the use of non-responder strain combinations. Cell-mediated immunity was assayed in a strain combination that is an unambiguous high responder, in which 100% of the females respond to the paternal strain by making alloantibodies. Maternal cell-mediated responses to paternal antigens were measured by the assays of DTH and IL-2 secretion under limiting conditions. We were unable to detect any cell-mediated immunity to paternal class I antigens even though the female produced copious quantities of alloantibody.

Graft-versus-host disease in the rat: cellular changes and major histocompatibility complex antigen expression in the liver

Cellular changes in the liver were studied during an acute lethal graft-versus-host (GVH) disease in relation to the expression of major histocompatibility complex (MHC) antigens on different liver cells. Screening for MHC antigen expression revealed that control livers contained very few Ia+ cells: mainly cells in the portal tract interstitium and a small percentage of the Kupffer cells. The changes during an ongoing GVH reaction could be separated into those related to the sinusoid-associated cells, including the liver parenchyma, and those related to the portal-tract-associated cells, including periportal hepatocytes. In the sinusoids an increase in the number of Kupffer cells was seen, now all expressing Ia antigens. No damage to hepatocytes or other sinusoid-associated cells was observed. It is postulated that the increase in both number and Ia expression of the Kupffer cells is most probably due to an increased phagocytic uptake of blood-borne cellular debris and is not a result of extensive damage to hepatocytes. In the portal tracts expanding infiltrates were found composed of Ia+ T cells and macrophages (ratio 2:1). These infiltrates are probably due to a local accumulation of lymphocytes and macrophages as a result of an interaction of migrating donor-type alloreactive T cells with recipient type Ia+ cells present in the portal tract interstitium, which also interfered with normal recipient lymphocyte and macrophage traffic. Damage to portal-tract-associated cells was slight and confined to bile duct epithelial cells, which now expressed Ia antigens, and to periportal hepatocytes. In conclusion, these data do not indicate that damage to liver parenchyma plays a major role in the pathogenesis of an acute GVH reaction.

Secondary delayed type hypersensitivity to H-2 subregion-coded alloantigens

Secondary type delayed type hypersensitivity (DTH) in mice against class I alloantigens or non-H-2 alloantigens is characterized by an earlier appearance of DTH reactivity after booster immunization compared with the development of DTH reactivity after primary immunization. In contrast to the primary and secondary DTH against class I or non-H-2 alloantigens, the development of secondary DTH against class II alloantigens or a set of alloantigens that includes class II alloantigens is not faster than the development of primary DTH. Thus, primary and secondary immunization with class II alloantigens prevents secondary type DTH reactivity to simultaneously administered class I alloantigens and non-H-2 alloantigens.