CD20 is widely expressed on B cells, from early pre-B cells to later in differentiation, but it is absent on terminally differentiated plasma cells. Although the function of CD20 is unknown, it may play a role in Ca2+ influx across plasma membranes, maintaining intracellular Ca2+ concentration and allowing activation of B cells. Rituximab is relatively ineffective in elimination of cells with low CD20 cell-surface levels. It tends to stick to one side of B cells, where CD20 is, forming a cap and drawing proteins over to that side. The presence of the cap changes the effectiveness of natural killer (NK) cells in destroying these B cells. When an NK cell latched onto the cap, it had an 80% success rate at killing the cell. In contrast, when the B cell lacked this asymmetric protein cluster, it was killed only 40% of the time.The following effects have been found:
The Fc portion of rituximab mediates antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). Rituximab has a general regulatory effect on the cell cycle. Preferential elimination of malignant B cells with high CD20 levels and high BCR signaling propensity, especially in chronic lymphocytic leukemia (CLL). It increases MHC II and adhesion molecules LFA-1 and LFA-3 (lymphocyte function-associated antigen). It elicits shedding of CD23. It downregulates the B cell receptor. It induces apoptosis of CD20+ cells.
Specifically variants in G1 and G2 of apolipoprotein L1 in the African American have shown increased risk of albuminuria, and hyperfiltration. Environmental
Risk factors for papillary necrosis include analgesics, concomitant cirrhosis, diabetes, pyelonephritis, systemic vasculitis, renal vein thrombosis, and urinary tract obstruction. Diagnosis
Diagnosis is done through the exclusion of other potential causes. These include acute tubular necrosis from chronic ischemia, membranoproliferative glomerulonephropathy from hepatitis C, nephrolithiasis causing obstructive nephropathy, and papillary necrosis which could be caused by pyelonephritis, diabetes mellitus, or from NSAIDs. The use of renal biopsy is not necessary unless there is a sudden onset of large protein excretions or signs of rapidly declining renal function. Urinalysis, microalbumin to creatinine ratio, quantification of urine protein and ultrasound (to exclude obstructive nephropathy and detect papillary necrosis) are methods used to determine renal function. Early signs include abnormally large and distended glomeruli causing hyperfiltration from as young as two years old. Albuminuria has been used for initial diagnosis in children from as young as four years old but significant damage may have already occurred by the time albuminuria has been detected. Creatinine measurements may not always be accurate because while the glomerulus completely filters creatinine, secondary secretion in the proximal tubules is maximally utilized in those with SCD so GFR may appear to be higher than what it actually is. If exhibiting hematuria, a CT scan should be done to exclude medullary carcinoma and due to multiple blood transfusions, serologies of the autoantibody and complement levels of HIV, hepatitis B and C should also be done.