Low density lymphocytes: their relationship to disease activity and to antirheumatic therapy.

The acquisition of low density by lymphocytes is the earliest detectable marker of their activation and may be utilized for the separation and quantification of these cells. Low density lymphocytes (LDL) are found in increased numbers in patients with rheumatoid arthritis compared with healthy controls (p less than 0.05). The number of LDL is raised in patients who failed to respond clinically to gold or D-penicillamine when compared with those who did respond (p less than 0.05), the latter group having LDL values in the normal range. Sequential studies have shown that successful antirheumatic therapy is associated with a return to normal LDL levels (p less than 0.01) and that any alteration occurs by three months. LDL are particularly associated with synovitis and there was a close correlation (p less than 0.01) with the Compound Thermographic Index in the sequential study, as well as with other markers of synovitis, but not with systemic disease. LDL thus appear to be important markers of the synovitis of rheumatoid arthritis and they may represent a population of lymphocytes closely involved in the maintenance of synovial inflammation.