Autoimmunity is an example of the potent and destructive function expressed by the immune system when normal constraints against self reactivity are lost or compromised. The study of mechanisms providing insight into the development of AI is not only of great clinical importance, but, moreover, may yield important insights into the manner in which control over immune function is normally regulated. This proposal has developed from findings, both our own as well as those of others, that have revealed a dramatic defect in cytokine (CK) expression in macrophages (mphi) from autoimmune- prone (AIP) mice.
The specific aims are directed towards an understanding of the potential relationship of this defect to the development of autoreactivity, as well as defining the molecular basis of this dysregulation. The potential importance of this observation is supported by the findings that the defect is among the earliest known immunological problems in AIP mice, and appears to be diagnostic for strains associated with lupus-like disease. Moreover, critical involvement of CK in the regulation of lymphocyte growth and function is well-documented.
The specific aims are (1) to evaluate CK production in vivo and in vitro, and relate it temporally and anatomically to the development of autoreactive T cells (ART). We will (a) determine CK mRNA and protein content in mphi isolated from a number of tissues during several stages of ontogeny of N and AIP mice; (b) quantitate ART by limiting dilution, and compare to the induction of KLH-reactive T cells, to determine if there is an association of ART development with endogenous regulation of CK, and if the response to self and foreign ags is similar; (c) study the in vivo induction of CK, using cloned ART as a stimulus; (d) study AIP --> N chimera to determine if the mphi defect is truly intrinsic; (2) to determine how the defective process of CK expression is initiated. We will (a) define the role of adherence in the aberrant regulation of CK in AIP mphi. In particular, we will evaluate pathways which might account for such regulation in situ, ie, interaction of these mphi with ART or extracellular matrix proteins; (b) evaluate signal transduction in N and AIP mphi, focusing initially on two pathways that may relate to the events that we have observed: the differential regulation of IL-1 and TNF by specific kinases, and the adherence-mediated induction of cellular proto-oncogenes; and (3) to characterize the mechanism(s) which account for the aberrant regulation of CK genes in mphi from AIP mice. The mechanism(s) accounting for the limited and transient expression of CK mRNA in MRL/+ mphi will be determined by (a) transcriptional elongation and attenuation (by nuclear run on analysis), and (b) mRNA stability (using an in vitro mRNA decay system) at various times following the stimulation of the mphi. The role of newly synthesized proteins in these processes will also be examined. We believe that this approach should identify key aspects of the in vivo regulation of CK expression in AIP animals and its correlation with both the development of ART and the progression of disease.
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