THE ARRIVAL OF CELLS FROM THE SKIN TO THE LYMPH NODES IS SEVERELY AFFECTED IN AGED MICE.

RÓPOLO, B MALETTO, D. ALIGNANI, MC. PISTORESI-PALENCIA.

Punta del Este

Congreso; V Congreso Latinoamericano de Inmunología; 1999

Aging is accompanied by a series of dysfunctions of the immune system, manifested by a decline in immune response to exogenous antigens and an increased response to autoantigens (Immunology Letter. 40:243-250; 1994). Antigen presenting cells (APC) are essential for T and B cell activation, and play a determinant role in the regulation of the immune response. In order to study the APC function in aged mice, we immunized 3 (young) and 12-18 months old (aged) mice with OVA-CFA. Ten days after the third immunization, we injected OVA labeled with fluorescein isothiocyanate (FITC) or PBS (control) in the hind footpads of mice; six hours later we analyzed by flow citometry the cells presents in the popliteal lymph nodes. We found that young mice had a percentage of OVA-FITC positive cells of 33 ± 4 %, in aged mice just 18 ± 2 % were positive (p<0,005).and in control mice: 2 ± 0,5 % (p<0,005). Most of OVA-FITC positive cells were also CD11b+ (Mac-1 a chain). The percentages of double positive cells were 1% in control, 24% in young and 12% in aged mice. Forward vs. scattered analysis revealed a new population in lymph nodes of OVA-FITC injected mice, which is not seen in control lymph nodes (control mice: 2 ± 0,5% ; young mice: 27 ± 4% and 12-18 month-old mice: 16 ± 1 %. p<0.005). This new population consists of large, granular cells. As this population only appear in the lymph nodes of OVA-FITC injected mice, we suggested that they are cells coming from the site of the injection of the antigen, in this case the skin. In conclusion, in OVA immunized mice is recruited a new population (mainly CD11b+) of APC, able of uptake and transport OVA from the skin to the lymph node. In aged mice, this new population is severely diminished, which could count for the dysfunctions of immune response observed in aged organisms. (Grants: CONICET. CONICOR. SeCyt UNC.)